Military Hans Högman
Copyright © Hans Högman 2020-12-18

Aircraft Warning Service 1939 - 1945

Air Defense, Sweden

Under the 1936 Defense Act, a nationwide Aircraft Warning and Alarm Service was established. During WWII 1939 - 1945, the Swedish Air Defense stood on four legs: the aircraft warning service, anti-aircraft defense, fighter aircraft, and the Civil Defense. In an enemy air raid, the Aircraft Warning Service detected the enemy planes and triggered off a flash message. The anti-aircraft defense in the concerned areas set off anti-aircraft firing when the enemy aircraft were within shooting range. The Air Force fighters took off to intercept the approaching bombers. Meanwhile, the civil defense set off the air-raid warning sirens and opened the shelters. During WWII, the Army was responsible for the Aircraft Warning Service and alerted the Anti-aircraft Defense and the Air Force for combating and the Civil Defense for the protection of the civilian population. Besides the Army aircraft warning service, the Air Force also had some aircraft warning service. Sweden was a non-belligerent state and not directly involved in the combats of WWII. However, the war nevertheless had a great effect on the population of Sweden. Rationing was imposed for example. During WWII Sweden mobilized its armed forces and men of draft-age were called up for military service for long periods.

Aircraft Warning Service in Sweden

The Aircraft Warning Service was a service carried out by the Swedish Army to keep watch for enemy planes entering Swedish airspace. Sweden was split into several regional aircraft warning zones and within each zone, Aircraft Warning Centers (Swe: Luftbevakningscentral) were established in strategic, but secret, locations. Further, each aircraft warning zone consisted of many Aircraft Observation Posts (Swe: Luftbevakningsstation). At each observation post served between 5 and nine ground aircraft observers. Both men and women served as Ground Aircraft Observers (Swe: Luftbevakare), about a third of the aircraft observers were women. These women were members of the Swedish Women’s Voluntary Defense Service, known as the Swedish Lotta Corps (Swe: Lottakåren). The aircraft observers were organized by aircraft warning companies. Each company was part of an aircraft warning battalion. There was one aircraft warning battalion per aircraft warning zone. Some aircraft warning units were organized by the Navy. The aircraft observation posts’ duty was to watch for aircraft in their designated area and set off flash message to their respective Aircraft Warning Center, independent if it was a Swedish or enemy aircraft. Each post had its own code name and number. When aircraft were spotted, the volunteer observers would record their observations on forms or in logbooks and then quickly place a call to their Aircraft Warning Center and verbally deliver a "Flash Message" which contained the organized data from the observation. One can imagine that aircraft approaching the coast would be spotted by multiple posts, resulting in multiple Flash Messages and, therefore, a reasonably accurate triangulation of position, speed, direction, altitude, etc. The image to the left shows three members of the Lotta Corps on duty at an aircraft warning center in Karlskoga, receiving aircraft warning flash messages during WWII. Image: Inger Frisk’s photo album. Many of the aircraft observation posts were filled with female observers only, keeping watch for enemy planes up in high wooden towers. The female observers were therefore nicknamed “tornsvalor” which literally means “tower swallows” and is the Swedish name of a bird. In English, this bird is called “Swift”. Along the coasts, several hundred observation posts were established. However, observation posts were not only established on the coasts. A nationwide network of aircraft observation posts was established, i.e., also in the interior of Sweden. In the beginning of WWII, the aircraft observers were placed in high buildings, such as church towers, lighthouses, silos, etc. However, as the war escalated, high wooden towers were constructed, so- called aircraft observation towers (Swe: Luftbevakningstorn), at each observation post. The locations of the observation posts were secret. At the beginning, the aircraft observers were quartered in nearby homesteads, farms, etc. where they received board and lodging. However, soon, at each observation post, a barrack was built for the personnel serving at the observation post, with bunks, toilet, and cooking facilities. The aircraft observation towers were timber constructions with an elevation between 15m and 25m (49 to 82 ft.). The towers were wider at the base and narrowing off at the top. At the top of the tower was a fenced observation deck. The sketch to the left shows an aircraft observation tower with the observation deck at the top, above the treetops. There had to be full visibility between the top of the tower and the barrack so that the head of the aircraft observation post could have eye contact with the observer up in the observation tower from his office in the barrack. The crew at each aircraft observation post consisted of a commanding officer (Swe: Luftbevakningschef), a deputy, a cook, and several volunteer aircraft observers, usually 9 observers. The observers were divided into 3 shifts and each shift consisted of: an optical lookout post, a sound locater post, and a telephone post. The two first served up in the tower. The telephone post was responsible for placing the call to the regional Aircraft Warning Center once a plane was spotted and verbally deliver a "Flash Message". Each shift of observers was on their stand for two or four hours, around-the-clock service. Each crew of aircraft observers served between 6 to 12 weeks and was then replaced by another crew. The image to the right shows a female aircraft observer with the Lotta Corps on duty at an aircraft observation post in the vicinity of Södertälje during WWII. Image: Försvarsstabens pressdetalj (1941).

Women’s Voluntary Defense Service - Lotta Corps

The Swedish Lotta Corps (Swe: Svenska Lottakåren (SLK)) was a women’s voluntary auxiliary defense services established in 1924. The women who served as aircraft observers were members of the Lotta Corps. The women serving as aircraft observers were dressed in army uniforms. In 1942, the women’s voluntary defense service got its first own women’s military uniform, uniform m/1942 kv. This uniform was designed with the Swedish battledress m/1939 as a prototype. The women’s uniform m/1942 was made of gray-brown- green woolen cloth. For information, see Military Uniforms for the Women’s Voluntary Defense Services and The Swedish Lotta Corps (Lottakåren)

Aircraft Warning Centers

Under the 1936 Defense Act, a nationwide Aircraft Warning and Alarm Service was established. The nation was subdivided into 18 Aircraft Warning Regions (Luftbevakningsområden (lbo)) and within each such region, an Aircraft Warning Center (AWC) (Luftbevakningscentral (lc)) was established. Each AWC had several Aircraft Observation Posts (AOP) (Luftbevakningsstation (ls)) reporting aircraft observations once spotted, i.e., so-called “flash messages”. The AWC:s processed the data from the observation posts. Center personnel represented the information from the flash messages designations on markers placed on large regional plotting maps in windowless rooms in rock shelters. As the war escalated, the number of aircraft observation post increased rapidly. In some regions, the AWC:s was overloaded with all the flash messages from the observation posts, and the processing of the data was sometimes delayed. To avoid this problem, some aircraft warning regions were split in two and new Aircraft Warning Centers were established. Most AWC:s had a twin center; if an AWC was eliminated in an air-strike, the aircraft warning service could soon continue in the designated, prepared twin center. The mobile AWC:s were called Reserve Aircraft Warning Centers. Further, Mobile Aircraft Warning Centers were also established. The mobile AWC:s were set up in specially equipped buses. Each mobile AWC consisted of two buses. The buses were supplied with equipment so they could connect to the telephone network.

Aircraft Observation Posts

Each Aircraft Warning Center (AWC) had several Aircraft Observation Posts attached. The observation posts were carrying out optical and audiovisual surveillance of the airspace. When aircraft were spotted, the volunteer observers would record their observations in number code on special forms and then quickly place a telephone call to a regional Aircraft Warning Center and verbally deliver the coded "Flash Message", which contained the organized data from the observation, to a telephone operator at the Center. Initially, the Aircraft Warning Service did not dispose of any telephone network of their own but used the public network with manual switchboards. However, the flash message calls from the aircraft observation posts were prioritized. Aircraft observation posts in locations without a public telephone network delivered their flash messages over the radio. The Aircraft Warning Centers were (information and filter centers) and center personnel processed the information from the delivered flash messages. Besides the military staff, the bulk of the center personnel were women from the Women’s Voluntary Defense Service. When a telephone operator at a Center received a flash message from an aircraft observer, she noted the message in the same code on a corresponding form in two copies. The received messages were then passed on to the AWC Dispatch Room where a dispatcher ordered the incoming flash messages date and time order and forwarded one copy to the alert officer on duty who decoded the flash messages and took the call to whether to alert the civil defense or not. If the flash messages would induce an alert this was done by remote control for the concerned area. Then, female volunteer Center personnel represented the information from the flash messages designations on markers placed on large regional plotting maps. The second copy of the flash message was forwarded to a briefing officer who took the call whether to alert the anti-aircraft defense, the Air Force airbases in the concerned area, and army ground troops.

Women’s Aircraft Warning Service - Lotta Corps

The female aircraft observes were nicknamed “tornsvalor” which means “tower swallows” since they served up in observation towers. The nickname arose when Swedish reporters wrote articles about the female volunteer aircraft observers in newspapers and a witty reporter came up with the nickname “tornsvalor”. Both men and women served as voluntary aircraft observers. However, the aircraft observation posts either consisted of pure male crews or pure female crews, never mixed. The female observers were foremost recruited through ads in newspapers. Both the male as well as the female observers were equipped with military uniforms, initially with the army battledress m/1939. In 1942, the first military uniform specially designed for women was adopted, uniform m/1942 kv. See the image to the right. Many countries used female volunteers within their Aircraft Warning Service, including female observers. However, in Sweden, the female aircraft observers were armed, which was unusual. They were equipped with army rifle m/1896, ammunition belt, bayonet, and 20 live cartridges. On duty, the observers were carrying out optical / audiovisual surveillance of the airspace on the observation towers. When aircraft were spotted they delivered a flash message to the AWC. The volunteers were also carrying out guard duties as sentries. Then female volunteers were assisted by a guard dog. The dogs were supplied from the Army K9 Center in Sollefteå. The observers were divided into 3 shifts and each shift consisted of: an optical lookout post, a sound locater post, and a telephone post. Each shift of observers was on their stand for two or four hours, around-the-clock service. At the end of 1940, about 20,000 volunteers served as aircraft observers. All observers received extensive training in aircraft recognition. They were also equipped with flashcards with silhouette images of aircraft to simplify the recognition of the planes; enemy planes and Swedish. The observers were also equipped with a pair of binoculars, a pelorus (direction finder), and maps over the terrain, bearing compass, stop-watch, etc. They were even equipped with sunglasses to avoid the dazzling sun while watching out for planes on sunny days. The image to the right shows an aircraft observer with the Lotta Corps on duty at an aircraft observation post, fixing the position to an aircraft with a direction finder during WWII. The observers served high up in wooden towers for best visibility. The female aircraft observers were therefore nicknamed “tornsvalor which literally means “tower swallows” and is the Swedish name of a bird. In English, this bird is called “Swift”. Image: Krigsarkivet. During nights and days with poor visibility, the observers must watch for sounds from aircraft engines. By the time the observers became very skilled in recognizing the sound of different aircraft. They were able to identify the type of aircraft, direction, and speed by listening to the sound. It happened frequently that foreign aircraft entered Swedish airspace during the war and Soviet aircraft, for example, dropped bombs over Sweden several times. A secondary duty for the observers was to deliver weather reports and alerts in case of spotted forest fires. The image to the left shows a female aircraft observer with the Lotta Corps watching out for aircraft at an aircraft observation post near Södertälje during WWII. Image: Försvarsstabens pressdetalj (1941). From 1940, the aircraft observers could advance to the ranks of Sergeant and Staff Sergeant. Later during the war, they were able to advance to Second Lieutenant. However, Female officers were only permitted to be in command of other females, not men. About a third of all aircraft observers were women. Before the women could serve as observers they first had to undergo training with the Lotta Corps (Women’s Voluntary Defense Service, SLK).

Armed Volunteer Aircraft Observers

The Swedish female aircraft observers were armed. They were equipped with army rifle m/96 and live ammunition and they were permitted to open fire if being attacked. Armed aircraft observers were very unusual compared to other countries. The observers weren’t armed in countries such as the USA and the UK although these countries were involved in WWII. It happened that the female Swedish observers were forced to fire warning shots to keep ”naughty boys and young men” away, who in lack of judgment tried to climb up to the female observers in the towers. The image to the right shows a female aircraft observer with the Lotta Corps on duty at her observation tower, armed with field glasses, ammunition belt, and a loaded rifle during WWII. Image: Krigsarkivet.

Radar Surveillance of the airspace

During WWII, Sweden had no operational radar surveillance systems. Before WWII, researchers in several countries, independently and in great secrecy, developed technologies that led to the modern version of radar. In the 1940s, a key development was the cavity magnetron in the UK, which allowed the creation of relatively small systems with sub-meter resolution. Britain shared the technology with the USA. The information provided by radar includes the bearing and range (and therefore position) of the object from the radar scanner. The first use of radar was for military purposes: to locate air, ground, and sea targets. The radar system provided the vital advanced information that helped the Royal Air Force win the Battle of Britain. The war precipitated research to find better resolution, more portability, and more features for radar. In Sweden, researchers were experimenting with radar. However, the armed forces needed radar during the war and a way to speed up the access to operational radar was to acquire radar from the US or the UK. The first radar system in Sweden was the Er2b and Er3b. “Er” stands for “Echo Radio”.

Images

Further below, are a few images from a photo album made by Karin Nordberg in memory of her time as a volunteer aircraft observer at an aircraft observation post near Jokkmokk, North Sweden, between January and March 1942, i.e., during WWII. She volunteered as an observer during the war and in January 1942 she began her service with the 91st Aircraft Defense Company in Tellejokk, Kåbdalis, between Arvidsjaur and Jokkmokk, Lapland, North Sweden. Karin Elisa Maria Nordberg was born on 14 May 1922 in Karlstad, Värmland. On 23 June 1946 she married Per Johan Berglund.
The two sketches show an example of an aircraft observation post with the tower and observation deck and the adjacent barrack. The second sketch shows the observation deck with an aiming instrument - direction finder (Syftinstrument), maps (syftkarta) etc. Sketches: ”Instruktion för luftbevakningsstation”, 1943. These images show two examples of so-called flash messages from an observation post to an Aircraft Warning Center. The left message concerns a major air-strike and the right message a landing of airborne troops. The data on the flash messages were coded. Images: FHT. Two female aircraft observers crosscutting firewood.Image: Krigsarkivet. Female aircraft observer fixing the position to an aircraft with an direction finder. Image: Krigsarkivet. An female aircraft observer on duty . Image: Flygvapenmuseum, ID: FVMF.002402. Two female observers at a observation tower during the winter of 1942 wearing uniforms and armed with rifles. From left; Birgit Johansson and Karin Nordberg. The aircraft observation post was located in Tellejåkk, Kåbdalis, Lapland. Photo album, Karin Nordberg. Image: Flygvapenmuseum, ID: FVMF.004427. Aircraft observer Karin Nordberg wearing her uniform and rifle, winter of 1942. Photo album, Karin Nordberg. Image: Flygvapenmuseum, ID: FVMF.004434. Two female aircraft observers, Inger (surname unknown) and Karin Nordberg ski patrolling, winter of 1942 in Tellejåkk, North Sweden. Photo album, Karin Nordberg. Image: Flygvapenmuseum, ID: FVMF.004443. An Aircraft Warning Center in Karlskoga during WWII, rock shelter. Photo: Inger Frisk photo album. The exterior of an aircraft observation post’s barrack in Tellejåkk, Kåbdalis, North Sweden,  in 1942. In this case, the observation deck is built on top of the roof. A female observer is on duty on the deck.  Photo album, Karin Nordberg, aircraft observer during WWII. Image: Flygvapenmuseum, ID: FVMF.004424.
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Militaria Hans Högman
Copyright © Hans Högman 2020-12-18

Aircraft Warning Service

1939 - 1945

Air Defense, Sweden

Under the 1936 Defense Act, a nationwide Aircraft Warning and Alarm Service was established. During WWII 1939 - 1945, the Swedish Air Defense stood on four legs: the aircraft warning service, anti- aircraft defense, fighter aircraft, and the Civil Defense. In an enemy air raid, the Aircraft Warning Service detected the enemy planes and triggered off a flash message. The anti-aircraft defense in the concerned areas set off anti-aircraft firing when the enemy aircraft were within shooting range. The Air Force fighters took off to intercept the approaching bombers. Meanwhile, the civil defense set off the air- raid warning sirens and opened the shelters. During WWII, the Army was responsible for the Aircraft Warning Service and alerted the Anti-aircraft Defense and the Air Force for combating and the Civil Defense for the protection of the civilian population. Besides the Army aircraft warning service, the Air Force also had some aircraft warning service. Sweden was a non-belligerent state and not directly involved in the combats of WWII. However, the war nevertheless had a great effect on the population of Sweden. Rationing was imposed for example. During WWII Sweden mobilized its armed forces and men of draft-age were called up for military service for long periods.

Aircraft Warning Service in

Sweden

The Aircraft Warning Service was a service carried out by the Swedish Army to keep watch for enemy planes entering Swedish airspace. Sweden was split into several regional aircraft warning zones and within each zone, Aircraft Warning Centers (Swe: Luftbevakningscentral) were established in strategic, but secret, locations. Further, each aircraft warning zone consisted of many Aircraft Observation Posts (Swe: Luftbevakningsstation). At each observation post served between 5 and nine ground aircraft observers. Both men and women served as Ground Aircraft Observers (Swe: Luftbevakare), about a third of the aircraft observers were women. These women were members of the Swedish Women’s Voluntary Defense Service, known as the Swedish Lotta Corps (Swe: Lottakåren). The aircraft observers were organized by aircraft warning companies. Each company was part of an aircraft warning battalion. There was one aircraft warning battalion per aircraft warning zone. Some aircraft warning units were organized by the Navy. The aircraft observation posts’ duty was to watch for aircraft in their designated area and set off flash message to their respective Aircraft Warning Center, independent if it was a Swedish or enemy aircraft. Each post had its own code name and number. When aircraft were spotted, the volunteer observers would record their observations on forms or in logbooks and then quickly place a call to their Aircraft Warning Center and verbally deliver a "Flash Message" which contained the organized data from the observation. One can imagine that aircraft approaching the coast would be spotted by multiple posts, resulting in multiple Flash Messages and, therefore, a reasonably accurate triangulation of position, speed, direction, altitude, etc. The image to the left shows three members of the Lotta Corps on duty at an aircraft warning center in Karlskoga, receiving aircraft warning flash messages during WWII. Image: Inger Frisk’s photo album. Many of the aircraft observation posts were filled with female observers only, keeping watch for enemy planes up in high wooden towers. The female observers were therefore nicknamed “tornsvalor which literally means “tower swallows” and is the Swedish name of a bird. In English, this bird is called “Swift”. Along the coasts, several hundred observation posts were established. However, observation posts were not only established on the coasts. A nationwide network of aircraft observation posts was established, i.e., also in the interior of Sweden. In the beginning of WWII, the aircraft observers were placed in high buildings, such as church towers, lighthouses, silos, etc. However, as the war escalated, high wooden towers were constructed, so-called aircraft observation towers (Swe: Luftbevakningstorn), at each observation post. The locations of the observation posts were secret. At the beginning, the aircraft observers were quartered in nearby homesteads, farms, etc. where they received board and lodging. However, soon, at each observation post, a barrack was built for the personnel serving at the observation post, with bunks, toilet, and cooking facilities. The aircraft observation towers were timber constructions with an elevation between 15m and 25m (49 to 82 ft.). The towers were wider at the base and narrowing off at the top. At the top of the tower was a fenced observation deck. The sketch to the left shows an aircraft observation tower with the observation deck at the top, above the treetops. There had to be full visibility between the top of the tower and the barrack so that the head of the aircraft observation post could have eye contact with the observer up in the observation tower from his office in the barrack. The crew at each aircraft observation post consisted of a commanding officer (Swe: Luftbevakningschef), a deputy, a cook, and several volunteer aircraft observers, usually 9 observers. The observers were divided into 3 shifts and each shift consisted of: an optical lookout post, a sound locater post, and a telephone post. The two first served up in the tower. The telephone post was responsible for placing the call to the regional Aircraft Warning Center once a plane was spotted and verbally deliver a "Flash Message". Each shift of observers was on their stand for two or four hours, around-the-clock service. Each crew of aircraft observers served between 6 to 12 weeks and was then replaced by another crew. The image to the right shows a female aircraft observer with the Lotta Corps on duty at an aircraft observation post in the vicinity of Södertälje during WWII. Image: Försvarsstabens pressdetalj (1941).

Women’s Voluntary Defense Service - Lotta

Corps

The Swedish Lotta Corps (Swe: Svenska Lottakåren (SLK)) was a women’s voluntary auxiliary defense services established in 1924. The women who served as aircraft observers were members of the Lotta Corps. The women serving as aircraft observers were dressed in army uniforms. In 1942, the women’s voluntary defense service got its first own women’s military uniform, uniform m/1942 kv. This uniform was designed with the Swedish battledress m/1939 as a prototype. The women’s uniform m/1942 was made of gray-brown-green woolen cloth. For information, see Military Uniforms for the Women’s Voluntary Defense Services and The Swedish Lotta Corps (Lottakåren)

Aircraft Warning Centers

Under the 1936 Defense Act, a nationwide Aircraft Warning and Alarm Service was established. The nation was subdivided into 18 Aircraft Warning Regions (Luftbevakningsområden (lbo)) and within each such region, an Aircraft Warning Center (AWC) (Luftbevakningscentral (lc)) was established. Each AWC had several Aircraft Observation Posts (AOP) (Luftbevakningsstation (ls)) reporting aircraft observations once spotted, i.e., so-called “flash messages”. The AWC:s processed the data from the observation posts. Center personnel represented the information from the flash messages designations on markers placed on large regional plotting maps in windowless rooms in rock shelters. As the war escalated, the number of aircraft observation post increased rapidly. In some regions, the AWC:s was overloaded with all the flash messages from the observation posts, and the processing of the data was sometimes delayed. To avoid this problem, some aircraft warning regions were split in two and new Aircraft Warning Centers were established. Most AWC:s had a twin center; if an AWC was eliminated in an air-strike, the aircraft warning service could soon continue in the designated, prepared twin center. The mobile AWC:s were called Reserve Aircraft Warning Centers. Further, Mobile Aircraft Warning Centers were also established. The mobile AWC:s were set up in specially equipped buses. Each mobile AWC consisted of two buses. The buses were supplied with equipment so they could connect to the telephone network.

Aircraft Observation Posts

Each Aircraft Warning Center (AWC) had several Aircraft Observation Posts attached. The observation posts were carrying out optical and audiovisual surveillance of the airspace. When aircraft were spotted, the volunteer observers would record their observations in number code on special forms and then quickly place a telephone call to a regional Aircraft Warning Center and verbally deliver the coded "Flash Message", which contained the organized data from the observation, to a telephone operator at the Center. Initially, the Aircraft Warning Service did not dispose of any telephone network of their own but used the public network with manual switchboards. However, the flash message calls from the aircraft observation posts were prioritized. Aircraft observation posts in locations without a public telephone network delivered their flash messages over the radio. The Aircraft Warning Centers were (information and filter centers) and center personnel processed the information from the delivered flash messages. Besides the military staff, the bulk of the center personnel were women from the Women’s Voluntary Defense Service. When a telephone operator at a Center received a flash message from an aircraft observer, she noted the message in the same code on a corresponding form in two copies. The received messages were then passed on to the AWC Dispatch Room where a dispatcher ordered the incoming flash messages date and time order and forwarded one copy to the alert officer on duty who decoded the flash messages and took the call to whether to alert the civil defense or not. If the flash messages would induce an alert this was done by remote control for the concerned area. Then, female volunteer Center personnel represented the information from the flash messages designations on markers placed on large regional plotting maps. The second copy of the flash message was forwarded to a briefing officer who took the call whether to alert the anti-aircraft defense, the Air Force airbases in the concerned area, and army ground troops.

Women’s Aircraft Warning Service

- Lotta Corps

The female aircraft observes were nicknamed tornsvalor” which means “tower swallows” since they served up in observation towers. The nickname arose when Swedish reporters wrote articles about the female volunteer aircraft observers in newspapers and a witty reporter came up with the nickname “tornsvalor”. Both men and women served as voluntary aircraft observers. However, the aircraft observation posts either consisted of pure male crews or pure female crews, never mixed. The female observers were foremost recruited through ads in newspapers. Both the male as well as the female observers were equipped with military uniforms, initially with the army battledress m/1939. In 1942, the first military uniform specially designed for women was adopted, uniform m/1942 kv. See the image to the right. Many countries used female volunteers within their Aircraft Warning Service, including female observers. However, in Sweden, the female aircraft observers were armed, which was unusual. They were equipped with army rifle m/1896, ammunition belt, bayonet, and 20 live cartridges. On duty, the observers were carrying out optical / audiovisual surveillance of the airspace on the observation towers. When aircraft were spotted they delivered a flash message to the AWC. The volunteers were also carrying out guard duties as sentries. Then female volunteers were assisted by a guard dog. The dogs were supplied from the Army K9 Center in Sollefteå. The observers were divided into 3 shifts and each shift consisted of: an optical lookout post, a sound locater post, and a telephone post. Each shift of observers was on their stand for two or four hours, around-the-clock service. At the end of 1940, about 20,000 volunteers served as aircraft observers. All observers received extensive training in aircraft recognition. They were also equipped with flashcards with silhouette images of aircraft to simplify the recognition of the planes; enemy planes and Swedish. The observers were also equipped with a pair of binoculars, a pelorus (direction finder), and maps over the terrain, bearing compass, stop-watch, etc. They were even equipped with sunglasses to avoid the dazzling sun while watching out for planes on sunny days. The image to the right shows an aircraft observer with the Lotta Corps on duty at an aircraft observation post, fixing the position to an aircraft with a direction finder during WWII. The observers served high up in wooden towers for best visibility. The female aircraft observers were therefore nicknamed “tornsvalor” which literally means “tower swallows” and is the Swedish name of a bird. In English, this bird is called “Swift”. Image: Krigsarkivet. During nights and days with poor visibility, the observers must watch for sounds from aircraft engines. By the time the observers became very skilled in recognizing the sound of different aircraft. They were able to identify the type of aircraft, direction, and speed by listening to the sound. It happened frequently that foreign aircraft entered Swedish airspace during the war and Soviet aircraft, for example, dropped bombs over Sweden several times. A secondary duty for the observers was to deliver weather reports and alerts in case of spotted forest fires. The image to the left shows a female aircraft observer with the Lotta Corps watching out for aircraft at an aircraft observation post near Södertälje during WWII. Image: Försvarsstabens pressdetalj (1941). From 1940, the aircraft observers could advance to the ranks of Sergeant and Staff Sergeant. Later during the war, they were able to advance to Second Lieutenant. However, Female officers were only permitted to be in command of other females, not men. About a third of all aircraft observers were women. Before the women could serve as observers they first had to undergo training with the Lotta Corps (Women’s Voluntary Defense Service, SLK).

Armed Volunteer Aircraft Observers

The Swedish female aircraft observers were armed. They were equipped with army rifle m/96 and live ammunition and they were permitted to open fire if being attacked. Armed aircraft observers were very unusual compared to other countries. The observers weren’t armed in countries such as the USA and the UK although these countries were involved in WWII. It happened that the female Swedish observers were forced to fire warning shots to keep ”naughty boys and young men” away, who in lack of judgment tried to climb up to the female observers in the towers. The image to the right shows a female aircraft observer with the Lotta Corps on duty at her observation tower, armed with field glasses, ammunition belt, and a loaded rifle during WWII. Image: Krigsarkivet.

Radar Surveillance of the airspace

During WWII, Sweden had no operational radar surveillance systems. Before WWII, researchers in several countries, independently and in great secrecy, developed technologies that led to the modern version of radar. In the 1940s, a key development was the cavity magnetron in the UK, which allowed the creation of relatively small systems with sub-meter resolution. Britain shared the technology with the USA. The information provided by radar includes the bearing and range (and therefore position) of the object from the radar scanner. The first use of radar was for military purposes: to locate air, ground, and sea targets. The radar system provided the vital advanced information that helped the Royal Air Force win the Battle of Britain. The war precipitated research to find better resolution, more portability, and more features for radar. In Sweden, researchers were experimenting with radar. However, the armed forces needed radar during the war and a way to speed up the access to operational radar was to acquire radar from the US or the UK. The first radar system in Sweden was the Er2b and Er3b. “Er” stands for “Echo Radio”.

Images

Further below, are a few images from a photo album made by Karin Nordberg in memory of her time as a volunteer aircraft observer at an aircraft observation post near Jokkmokk, North Sweden, between January and March 1942, i.e., during WWII. She volunteered as an observer during the war and in January 1942 she began her service with the 91st Aircraft Defense Company in Tellejokk, Kåbdalis, between Arvidsjaur and Jokkmokk, Lapland, North Sweden. Karin Elisa Maria Nordberg was born on 14 May 1922 in Karlstad, Värmland. On 23 June 1946 she married Per Johan Berglund.
The two sketches show an example of an aircraft observation post with the tower and observation deck and the adjacent barrack. The second sketch shows the observation deck with an aiming instrument - direction finder (Syftinstrument), maps (syftkarta) etc. Sketches: ”Instruktion för luftbevakningsstation”, 1943. These images show two examples of so-called flash messages from an observation post to an Aircraft Warning Center. The left message concerns a major air-strike and the right message a landing of airborne troops. The data on the flash messages were coded. Images: FHT. An female aircraft observer on duty . Image: Flygvapenmuseum, ID: FVMF.002402. Female aircraft observer fixing the position to an aircraft with an direction finder. Image: Krigsarkivet. Two female observers at a observation tower during the winter of 1942 wearing uniforms and armed with rifles. From left; Birgit Johansson and Karin Nordberg. The aircraft observation post was located in Tellejåkk, Kåbdalis, Lapland. Photo album, Karin Nordberg. Image: Flygvapenmuseum, ID: FVMF.004427. Aircraft observer Karin Nordberg wearing her uniform and rifle, winter of 1942. Photo album, Karin Nordberg. Image: Flygvapenmuseum, ID: FVMF.004434. Two female aircraft observers, Inger (surname unknown) and Karin Nordberg ski patrolling, winter of 1942 in Tellejåkk, North Sweden. Photo album, Karin Nordberg. Image: Flygvapenmuseum, ID: FVMF.004443. Two female aircraft observers crosscutting firewood.Image: Krigsarkivet. An Aircraft Warning Center in Karlskoga during WWII, rock shelter. Photo: Inger Frisk photo album. The exterior of an aircraft observation post’s barrack in Tellejåkk, Kåbdalis, North Sweden,  in 1942. In this case, the observation deck is built on top of the roof. A female observer is on duty on the deck.  Photo album, Karin Nordberg, aircraft observer during WWII. Image: Flygvapenmuseum, ID: FVMF.004424.