However , when a German U-boat sank the British liner `` Lusitania '' in 1915 , with 128 Americans aboard , U.S. President Woodrow Wilson vowed , `` America is n't too proud to fight '' and demanded an end to attacks on passenger ships .
When a German U-boat sank the British liner `` Lusitania '' in 1915 there were 128 Americans aboard . U.S. President Woodrow Wilson vowed that `` America is n't too proud to fight '' .