<P> The same month, the French Commander - in - Chief, General Robert Nivelle, ordered a new offensive against the German trenches, promising that it would end the war within 48 hours . The 16 April attack, dubbed the Nivelle Offensive (also known as the Second Battle of the Aisne, after the area where the offensive took place), would be 1.2 million men strong, preceded by a week - long artillery bombardment and accompanied by tanks . The offensive proceeded poorly as the French troops, with the help of two Russian brigades, had to negotiate rough, upward - sloping terrain in extremely bad weather . Planning had been dislocated by the voluntary German withdrawal to the Hindenburg Line . Secrecy had been compromised and German aircraft gained air superiority, making reconnaissance difficult and in places, the creeping barrage moved too fast for the French troops . Within a week the French suffered 120,000 casualties . Despite the casualties and his promise to halt the offensive if it did not produce a breakthrough, Nivelle ordered the attack to continue into May . </P> <P> On 3 May the weary French 2nd Colonial Division, veterans of the Battle of Verdun, refused orders, arriving drunk and without their weapons . Lacking the means to punish an entire division, its officers did not immediately implement harsh measures against the mutineers . Mutinies occurred in 54 French divisions and 20,000 men deserted . Other Allied forces attacked but suffered massive casualties . Appeals to patriotism and duty followed, as did mass arrests and trials . The French soldiers returned to defend their trenches but refused to participate in further offensive action . On 15 May Nivelle was removed from command, replaced by Pétain who immediately stopped the offensive . The French would go on the defensive for the following months to avoid high casualties and to restore confidence in the French High Command, while the British assumed greater responsibility . </P> <P> On 25 June the first US troops began to arrive in France, forming the American Expeditionary Force . However, the American units did not enter the trenches in divisional strength until October . The incoming troops required training and equipment before they could join in the effort, and for several months American units were relegated to support efforts . In spite of this, however, their presence provided a much - needed boost to Allied morale, with the promise of further reinforcements that could tip the manpower balance towards the Allies . </P> <P> In June, the British launched an offensive in Flanders, in part to take pressure off the French armies on the Aisne, after the French part of the Nivelle Offensive failed to achieve the strategic victory that had been planned and French troops began to mutiny . The offensive began on 7 June, with a British attack on Messines Ridge, south of Ypres, to retake the ground lost in the First and Second battles in 1914 . Since 1915 specialist Royal Engineer tunnelling companies had been digging tunnels under the ridge, and about 500 t (490 long tons) of explosives had been planted in 21 mines under the German defences . Following several weeks of bombardment, the explosives in 19 of these mines were detonated, killing up to 7,000 German troops . The infantry advance that followed relied on three creeping barrages which the British infantry followed to capture the plateau and the east side of the ridge in one day . German counter-attacks were defeated and the southern flank of the Gheluvelt plateau was protected from German observation . </P>

Kept german and french troops in a stalemate position on the western front