their Sussex pledge (not to sink merchant ships without due warning and to save human lives wherever possible) and began an unrestricted U-boat campaign on 1 February 1917. Since it was obvious that US shipping would also come under attack in the course of this operation, it became just a matter of time before the USA was drawn into the conflict.

Germany had been pursuing various interests in Mexico since the beginning of the 20th century. Although a latecomer in the