What forced Russia to discontinue fighting in World War 1?

Russia discontinued fighting in World War I primarily due to internal turmoil and the Bolshevik Revolution in 1917. The severe strain of military losses, economic hardship, and social unrest led to widespread dissatisfaction with the Tsarist regime, culminating in the abdication of Tsar Nicholas II. The Bolshevik government, under Lenin, sought to withdraw from the war to focus on consolidating power and addressing domestic issues. This resulted in the signing of the Treaty of Brest-Litovsk in March 1918, which formalized Russia's exit from the conflict.