2 November 2010
Last updated at 12:00
Aeroplanes had only been flying for just over a decade when war broke out, giving soldiers the first opportunity to see the battlefield from the air - providing both information to officers and a record of the devastation that World War I caused.
Officially the Third Battle of Ypres, Passchendaele became infamous for the number of dead and the mud. There were 325,000 Allied and 260,000 German casualties. The village lay five miles from the starting point of the offensive.
After the battle, the photographers returned to Passchendaele in 1917 to a scene that is almost unrecognisable. The area had been turned into a wasteland of blood and mud. All that remained were the ruins of the church.
At the start of the Battle of the Somme, a mine was blown at 07.28 on July 1. The explosions constituted what was then the loudest man-made sound in history and could be heard in London. It created the Lochnagar Crater - 90 yards across and 70 feet deep.
By the end of the day, the British had suffered 60,000 casualties, of whom 20,000 were dead. It was their largest loss in a single day. Around 60% of all officers involved on the first day were killed.
At the start of the war, airman on reconnaissance missions carried photographic equipment but no weapons. There are stories of German and British pilots waving at each other when passing in the air. That soon changed.
The cameras were basic and unwieldy and had to be used of heights at around of 12,000ft whilst leaning out of the aircraft, making it very difficult to take stable photographs.
Sometimes the photography helped identify enemy barracks. On first inspection, there is no real evidence to suggest that any of the buildings camouflaged under the trees were occupied.
But, as seen in this image enhanced by CGI, the flowerbeds in the centre of the picture were the giveaway that the buildings were still occupied by enemy forces.
Once the base was discovered, big guns were directed onto the position. The barracks (top, left of centre) have been destroyed and many shell craters can be seen throughout the surrounding area. The First World War from Above, BBC One, 9pm Sun 7 Nov.