The Germans' use of unrestricted submarine warfare against the merchant and passenger ships lead to the United States joining allies in WWI. The US had not a chance fighting the Germans alone.
Pearl Harbor
the Germans' use of unrestricted submarine warfare
Take over for Hitler and join Allies in fighting Russia
it finally realized what Germany was doing and the central powers were fighting for
Barbarossa
They had a treaty which obligated them to help their allies, France and Russia, and they decided to honour it. They were also fearful of Germany and thought it to be a threat to their own naval development in Europe.
The Allies
They wre allies of the affected
france
1914
yo face
I'm in Y5 but I do yr 7 work so: yes, berlin did join the Allies in WW2 in 1941