Why did america drop the atomic bomb on japan ?

President Harry S. Truman, warned by some of his advisers that any attempt to invade Japan would result in horrific American casualties, ordered that the new weapon be used to bring the war to a speedy end. On August 6, 1945, the American bomber Enola Gay dropped a five-ton bomb over the Japanese city of Hiroshima.

the treaty of brest-litovsk was a peace treaty signed on 3 march 1918 between the new bolshevik government of russia and the central powers (german empire, austria-hungary, bulgaria, and the ottoman empire), that ended russia's participation in world war i.