Submarines have resumed unconditional attacks on all Atlantic ships, including civilian passenger carriers. Although the United States feared a response, German military officials predicted that they could defeat their allies before the United States mobilized and armed troops to land in Europe. While Wilson was laying down his options on the submarine issue, he also had to consider whether Germany was trying to cement a secret alliance with Mexico. On 19 January 1917, the British Navy secret service decrypted and deciphered a telegram from German Foreign Minister Arthur Zimmerman to the German ambassador in Mexico City. The Zimmerman Telegram promised the Mexican government that Germany would help Mexico retake territory it ceded to the United States after the war between Mexico and the United States. In exchange for this aid, the Germans asked for Mexico`s support during the war. Gerard`s words proved to be correct when Germany announced on 1 February 1917 the resumption of the submarine war. Two days later Wilson announced a breakdown in diplomatic relations with the German government, and on April 6, 1917, the United States officially entered World War I on the Allied side. The blockade of the North Sea and the English Channel cut off the flow of war material, food and fuel to Germany during the First World War. Germany returned the favor with its submarines to destroy neutral ships that supplied the Allies.
The huge submarines (submarines) drifted the Atlantic armed with torpedoes. They were Germany`s only weapon of advantage, with Britain effectively blocking German ports for deliveries. The aim was to starve Britain before the British blockade defeated Germany. When the German Imperial Navy began its unrestricted submarine war campaign in 1915, naval operations were governed by existing war laws. The first set of these laws of war was founded at the second Hague Conference of 1907, whose treaties had been signed and ratified by the German Empire until 1909. The second Hague Conference sought to extend the principles set out at the first Hague conference of 1899 to the field of maritime warfare conduct, resulting in fourteen different conventions. Conventions VII, XI and XIII contain provisions directly or indirectly relevant to the settlement of unrestricted submarine warfare. Convention VII required that merchant ships turned into warships be controlled, expelled and registered as warships.