<P> At the 1911 meeting of the Institute of International Law in Madrid, legislation was proposed to limit the use of airplanes to reconnaissance missions and banning them from being used as platforms for weapons . This legislation was rooted in a fear that airplanes would be used to attack undefended cities, violating Article 69 of the Den Hague Reglement (the set of international laws governing warfare). </P> <P> At the start of the war, there was some debate over the usefulness of aircraft in warfare . Many senior officers, in particular, remained sceptical . However the initial campaigns of 1914 proved that cavalry could no longer provide the reconnaissance expected by their generals, in the face of the greatly increased firepower of twentieth century armies, and it was quickly realised that aircraft could at least locate the enemy, even if early air reconnaissance was hampered by the newness of the techniques involved . Early skepticism and low expectations quickly turned to unrealistic demands beyond the capabilities of the primitive aircraft available . </P> <P> Even so, air reconnaissance played a critical role in the "war of movement" of 1914, especially in helping the Allies halt the German invasion of France . On 22 August 1914, British Captain L.E.O. Charlton and Lieutenant V.H.N. Wadham reported German General Alexander von Kluck's army was preparing to surround the BEF, contradicting all other intelligence . The British High Command took note of the report and started to withdraw toward Mons, saving the lives of 100,000 soldiers . Later, during the First Battle of the Marne, observation aircraft discovered weak points and exposed flanks in the German lines, allowing the allies to take advantage of them . </P> <P> In Germany the great successes of the early Zeppelin airships had largely overshadowed the importance of heavier - than - air aircraft . Out of a paper strength of about 230 aircraft belonging to the army in August 1914 only 180 or so were of any use . The French military aviation exercises of 1911, 1912, and 1913 had pioneered cooperation with the cavalry (reconnaissance) and artillery (spotting), but the momentum was if anything slacking . </P>

When was the first plane used in ww1