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.
