What evidence does zinn provide to support his claims that the united states was motivated to enter the war for their business to make money to make money (besides german attacks in u. s. ships).

President W. Wilson had promised that the United States would stay neutral in the war. But in April of 1917, the Germans had announced they would have their submarines sink any ship bringing supplies to their enemies; and they had sunk a number of merchant ships. Wilson now said he must stand by the right of Americans to travel on merchant ships in the war zone.