Flying Fortresses winged their way over the fields after rural Norfolk became 'Little America'.

The county became a major springboard for the bombing offensive against Germany, after 50,000 US service personnel took part in the so-called friendly invasion of 1942.

Fields were concreted over to form runways for the B17 and B24 bombers which would take to the skies in daylight raids.

Eastern Daily Press: The shadows of bomber planes in flight dot the fields at RAF Watton The shadows of bomber planes in flight dot the fields at RAF Watton (Image: Historic England Archive (USAAF Photography))

They flew from 17 bases, to which more than 6,000 young men would not return from after being shot down by flak or enemy fighters.

Now aerial pictures taken during the latter years of the Second World War have been made accessible to the public for the first time.

Eastern Daily Press: Norwich from the air in 1944Norwich from the air in 1944 (Image: Historic England Archive (USAAF Photography))

They were taken by the United States Army Air Force's (USAAF) Photographic Reconnaissance (PR) units stationed at bases around the country in 1943 and 1944.

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Almost 4,000 black and white images showing England from the air are available in a free online, searchable map

Eastern Daily Press: Bassingbourn, in Cambridgeshire, where the B17 bomber Memphis Belle was basedBassingbourn, in Cambridgeshire, where the B17 bomber Memphis Belle was based (Image: Historic England)

They offer a unique view of the country as it changed during the Second World War.

The shadows of great bombers dot the fields around the now-defunct airbase at Watton.

Eastern Daily Press: Aerial towers and camouflaged huts at a radar station at Darsham, Suffolk, in August 1944 Aerial towers and camouflaged huts at a radar station at Darsham, Suffolk, in August 1944 (Image: Historic England Archive (USAAF Photography))

Towers reach into the sky from a radar station at Darsham, near Halesworth.

There are also hundreds of aerial views of towns and rural areas.

Eastern Daily Press: Castle Rising, near King's Lynn, almost obscured by cloudsCastle Rising, near King's Lynn, almost obscured by clouds (Image: Historic England Archive (USAAF Photography))

Pilots took photographs during flights over local areas near their bases while gaining the necessary experience to qualify for operations over enemy territory.

Flights were also made to test new and repaired aircraft and camera equipment, as well as to carry out photographic assignments.

Eastern Daily Press: Sandringham from the air in 1944Sandringham from the air in 1944 (Image: Historic England Archive (USAAF Photography))

America joined the Second World War in December 1941, following Japan’s attack on Pearl Harbour.

The first aircrews of the USAAF’s VIII Bomber Command - later known as the Eighth Air Force - arrived in Britain in early 1942.

Eastern Daily Press: Clouds over the Fens in 1944Clouds over the Fens in 1944 (Image: Historic England Archive (USAAF Photography))

While the RAF bombed by night, the Americans attacked by day in their heavily-armed aircraft.

The collection can be accessed at https://historicengland.org.uk/usaaf