Why did the cold war start

The Cold War began after the surrender of Nazi Germany in 1945, when the uneasy alliance between the United States and Great Britain on the one hand and the Soviet Union on the other started to fall apart. ... The Americans and the British worried that Soviet domination in eastern Europe might be permanent.

i thinl it is the 1st answer

united states reinforcements contributed greatly to three allied victories in france at: cantigny (first major american battle), argonne (the largest in the united states military history, involving 1.2 million american soldiers), and château-thierry (one of the first actions under general pershing).