The lusitania was in 1915 and was one of 3 ships sunk before unrestricted subwarfare was called off for the first time. It was NOT the reason for war. Wilson, despite the claims of him wanting to go to war, was really not a war monger. He favored the Entente, which is incredibly obvious. But the major reason that he went to war was over the resumption of unrestricted subwarfare. The Zimmerman note, which was done behind Wilson's back after he let the Germans use the American diplomatic wire to keep contact with their embassy's abroad (something I don't understand why some other posters claim was illegal), which Zimmerman then used to try to create an alliance against the US. Wilson saw this a major stab in the back, and rather rightly asked to go to war. But it only accelerated the time line for war, not caused it.
Quite. Indeed, by one of those ironies, Germany provoked Wilson to war at a time when he was
less pro-Allied than he had ever been since the whole thing started. Arguments about British "blacklisting" of US firms with links to the Central Powers, and other blockade measures, had brought Anglo-US relations to an all time low, so much so that an intelligent man like Colonel House thought war between America and the
Allies to be a serious possibility!! Wilson had upset his Secretary of State, Robert Lansing, by taking no action over the sinkling in late 1916 of the merchantmen
Marina and
Arabia, because both of these were armed. Since by now the vast majority of Allied ships were either armed or in process of being, this was close to abandoning his stand against the u-boat war as far as Allied (though not neutral) vessels were concerned. He and Lansing were still swapping memos about it on Jan 31, when Ambassador Bernstorff rendered it all moot by announcing full USW against all ships regardless of flag.
This was the crucial difference between 1917 and what had gone before. Hitherto, all American victims of the u-boat had been travelling on Allied vessels. However, from Feb 1917 even
American ships were deemed "fair game" and several were sunk in March, three going down on the 18th alone. With America's own ships coming under attack (and in some cases being armed for self-defence) a virtual state of undeclared war already existed. It would have been diffcult enough to avoid formal hostilities even without the ZT, but that surely put the tin lid on it.
Now, Germany saw the US supplying the Entente with money and munitions as de facto belligerency.
Another little "joke" is that this happened just when British imports from the US were being cut back due to financial constraints. Britain had run out of securities etc in the US to serve as collateral on loans raised there. Since unsecured loans were not on offer while America remained neutral, this drastically reduced Allied purchasing power there, and but for US entry into the War, the halting of loans might have reduced British imports more than the u-boats did.
And basically, there was a culture of gamblers that saw it as a last ditch effort or go under. However, no one had the balls to challenge the bullshit 'study' that the navy had done about the effects of the submarine campaign. Bethman-Hollweg had no choice but to go along with the effort, because he was trying to save his political career. The German people had been lied to and constantly told the Submarine was the wonder weapon that would win the war. They thought politics and weak wills held them back, when in fact they were not at useful and the US was a much more dangerous enemy. Bethman-Hollweg was a weak-willed person, because he only thought about his career instead of doing what was right for the nation. Indeed that was the problem of much of the nation's leadership. And it led them to ruin in WW1 and later WW2.
And because there was no obvious alternative. The Russian Revolution was still in the future, and to all appearence 1917 seemed likely to be 1916 only worse, with the Russian army getting steadily better armed and equipped, while the British would be larger and more experienced. It looked as if Germany was doomed to defeat. If they didn't look the naval gift horse in the mouth, it was because they were getting desperate.
In fairness, they weren't the only ones to see it this way. When Admiral Sims reached Britain in April 1917, Lord Jellicoe told him that unless some way could be found of defeating the u-boats, then Britain would have to surrender by November 1 - only three months later than the Germans' own calculation.
This also explains their recklessness about provoking the US. As they saw things, if USW succeeded, they would win the war in 1917, while if not they would lose it in 1917 - in either case long before America could intervene effectively. Like a lot of people on this message board they only looked at the number of soldiers America could field, and ignored the naval and especially economic strength which US support would bring to the Entente - not to mention the effect on morale.