After the Russian withdrawal from the conflict, the Germans brought back all their troops from the pacified Eastern Front to the west, by rail. They opened a breach of 50 kilometres, crushing the British forces they met on the way. However, they did not take advantage of this opening quickly enough. With the help of their assault tanks, the Allies, working together, were able to reconstitute the line. In two days, they took 17,000 men prisoner and seized 360 guns. The contribution of American troops had become decisive in the Allied victories.