How did Lenin's takeover in Russia affect German war strategy?

Answer 1

It gave Germany the chance to bring troops fighting in Russia to fight in Western Europe. This was a major factor how the rest of the war would fought. Surprisingly the increase of troops in France did not seem to make significant gains for Germany.

Answer 2

The Germans actively facilitated Lenin's return to Russia in order to further destabilize Russia and make it pull out of the war. The first revolution in February, 1917 had toppled the Tsar and his regime, but much to the chagrin of Germany the revolutionaries continued the war against Germany with full force. The Germans gambled (rightly, as it was to turn out) that for Lenin to establish Bolshevik power and defeat his Russian adversaries, he would need peace with Germany.

When Russia indeed did sue for peace, the Germans could then - as had been their intention behind the whole Lenin strategy all along - concentrate all their military power on the Western front and try to force the deadlock that had been existing there for years. They failed at that, however.

Answer 3

Lenin agreed to the Treaty of Brest-Litovsk to end Russia's involvement in World War 1.