Steel engraving. Military reconnaisance from the air was first carried out by Napoleon's Republican army during the French Revolutionary Wars (1789-1795) in 1794. A balloon was inflated with hydrogen and held in place by two cables. The French could then observe enemy battle tactics from a safe distance, giving them both a military and psychological advantage. This image shows the 'Entreprenant' balloon at the Battle of Fleurus in Belgium on 26 June 1794. This battle was of great strategic importance to the Revolution because it protected the road to Paris.
© Science Museum / Science & Society Picture Library