Who broke the stalement during world war 1 1917?

The stalemate during World War I was broken in 1917 primarily due to the entry of the United States into the war in April. The influx of American troops and resources provided a significant boost to the Allied powers, contributing to renewed offensives. Additionally, the Russian Revolution led to Russia's withdrawal from the war, allowing Germany to shift its focus to the Western Front, which altered the dynamics of the conflict. These developments ultimately set the stage for more active military engagements and a shift in momentum.