How did the russian revolution changed the course of the war

The Russian Revolution had a major effect on the final result of WWI. The overthrow of the czar and the implementation of the Provisional Government under Kerensky led Wilson to feel much better about supporting the Allied cause since the Kerensky government promised to be progressive in its reforms.

The Allies pressured the Kerensky government to stay in the war; this led to dissatisfaction with the soldiers fighting the war, and many of them turned to support Lenin and Trotsky's promise of getting out of the war at all costs. By early 1918, the Bolsheviks had taken power under the promise of getting Russia out of the war. This led to the treaty of Brest-Litovsk which allowed Germany to shift all of its forces on the Eastern Front to take on the French, British, and Americans in the West in the summer of 1918. The promise of a reinforced German army in the West led the Allies to pressure the Americans to put more forces in the field. The winner-take-all offensive led by the Germans in the summer and early fall of 1918 ultimately led to the collapse of the German army and the armistice in November 1918.

The Russian Revolution allowed the Germans to focus on the Western Front, and it also pressured the Americans to send more military and economic aid to the Allies. German soldiers who were in Russian POW camps were also infected with ideas of socialism and they pressured the German government to sign the armistice. The abdication of the Kaiser which led to the armistice in November 1918 was caused not so much by the failure of the German army in the field; rather, it was caused by the threat of another Bolshevik revolution happening in Germany. This unrest at home ultimately led to Germany's surrender.

With Russia out of the war, German generals saw a chance to win the war. So, in March 1918, the Russians signed the Treaty of Brest-Litovsk, a peace agreement between Russia and the Central Powers, and they were out of the war.