On June 9, 1915, United States Secretary of State William Jennings Bryan resigns due to his concerns over President Woodrow Wilson’s handling of the crisis generated by a German submarine’s sinking of the British passenger liner Lusitania the previous month, in which 1,201 people—including 128 Americans—died.

Germany’s announcement in early 1915 that its navy was adopting a policy of unrestricted submarine warfare concerned many within the government and civilian population of the United States—which maintained a policy of strict neutrality during the first two years of World War I. The sinking of the Lusitania on May 7, 1915, caused an immediate uproar, as many believed Germany had sunk the British cruiser deliberately as a provocation to Wilson and the U.S.

Bryan, as secretary of state, sent a note to the German government from the Wilson administration, lauding the ties of friendship and diplomacy between the two nations and expressing the desire that they come to a clear and full understanding as to the grave situation which has resulted from the sinking of the Lusitania. When the German government responded by justifying their navy’s action on the basis that the Lusitania was carrying munitions (which it was, a small amount), Wilson himself penned a strongly worded note, insisting that the sinking had been an illegal action and demanding that Germany cease unrestricted submarine warfare against unarmed merchantmen.

"The Government of the United States is contending for something much greater than mere rights of property or privileges of commerce," Wilson wrote. "It is contending for nothing less high and sacred than the rights of humanity, which every Government honours itself in respecting and which no Government is justified in resigning on behalf of those under its care and authority."

Objecting to the strong position taken by Wilson in this second Lusitania note, and believing it could be taken as a precursor to a war declaration, Bryan tendered his resignation on June 9, 1915, rather than sign it. The note and two more similar ones were sent to Germany, which was persuaded to curb the submarine policy over the course of 1916 rather than risk further antagonizing the U.S.

Bryan’s resignation marked a significant turning point, as the Lusitania crisis had convinced his successor, Robert Lansing, that the U.S. could not remain neutral forever, and would indeed eventually have to enter the war against Germany. As it unfolded, Germany resumed its policy of unrestricted submarine warfare in February 1917; two months later, Wilson went before Congress to ask for a declaration of war.