At the outbreak of WW1, balloons  served as platforms for aerial observation, albeit vulnerable ones with their hydrogen-filled bulks floating above the battlefield offering tempting targets.

As the war progressed, and photographic equipment evolved rapidly in response to the need for intelligence, dedicated reconnaissance aircraft were fitted with cameras able to return detailed images of the destruction below, such as the fate of the Belgian village of Passendale, erased from the map during the Third Battle of Ypres:

The watercolour by the Architect, Curt Ruschoff,  shows German soldiers recording the position of the Allies on the Western Front, plotted from Observation balloons. Smoke can be seen rising from shelling below.