Why did Russia's withdrawal from the war hurt the Allies?

Britain and france face what they did offensive from Germany after the Russians withdrew

The allies lost a major part of their Alliance. With Russia in the war, Germany and the Central Powers had to fight a 'two front' war. The Eastern (Russia and Germany) and Western front. (France and Germany) This made Germany split their troops in half and have less men on each side. With Russia out of the war they could mobilize all their troops to the Western front and focus on winning the war.