However, by May 1917, the sinking of the RMS Lusitania had been critical in changing a vast demographic of the American population against Germany, leaving the attitude towards Germany rocky at best, though an isolationist sentiment had still been present, as evidenced by President Woodrow Wilson’s promise to avoid war, which won him his re-election. When, two years after the loss of the Lusitania, the Reichstag approved the decision to resume unrestricted submarine warfare, all diplomatic ties were severed. The situation had been worsened with the discovery and decryption of the Zimmermann Telegram by the British Room 40 unit. The content of the telegram had been an explicit proposition to Mexico to aid Germany by declaring war on the U.S. if Germany is attacked by the Americans. This inept maneuver by the German foreign secretary had been a blatant threat against the United States, and in just over a month, the U.S. Congress had officially approved of the decision to declare war on Germany. The Zimmermann Telegram may be considered to be a vital short-term cause to the entrance of the Great War on the bounds that a sizable demographic had still been opposed to a declaration of war, especially since one of the largest ethnic groups of the United States were of German origin. Further evidence to support this may include …show more content…
entry into the war. The reason for this conclusion is based on the justifications primarily involved with the diplomatic strain subsequent of unrestricted submarine warfare. The sinking of the Cunard liner RMS Lusitania, having been mentioned several times before, is evidenced to have already placed the United States on the brink of war and causing the attitude of the American public to shift in favor of war. Furthermore, the severance of German-American relations due to the reintroduction of unrestricted submarine warfare supports the evidence of a strong shift of pro-war opinion amongst the America public. It may therefore be concluded that the unrestricted submarine warfare alone may have been capable of leading the United States into war. However, it may also be justified that with the strong isolationist attitude still present, the Zimmermann Telegram may have acted as simply a catalyst to the American entry of the war, as evidenced by the difficult opposition in the congress at the time of the vote to enter the war. Therefore, the Zimmermann Telegram is not inherently necessary for American entry into the