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.