I think the correct answer would be the second option. The Soviet Union joined the allies because Hitler had broken a pact and attacked. The pact was called the German-Soviet nonaggression pact. This pact was regarded by Hitler as a tactical move. It was signed on the year 1940 and after a year Hitler attacked the Soviet Union.
Answer:D
Explanation:The essay describes alot of the answer in D
Antietam, also called the Battle of Sharpsburg