German submarine warfare was one of the major reasons why the U. S. joined the Allies in WW I.

True or False?

The answer to this question is true.

5 Reasons for the US Entry into World War I

In response to Britain’s blockade, Germany turned to unrestricted submarine warfare to keep goods from reaching Britain. After the Sinking of the Lusitania, Germany promised to stop unrestricted submarine warfare but within less than one year, they torpedoed another passenger ship - the cross-English Channel ferry Sussex. Again, the Germans promised not to attack passenger ships without warning (the Sussex Pledge). But that pledge was short lived as well.

the answer is true