The veto was the result of extensive discussion during the negotiations for the formation of the United Nations at Dumbarton Oaks (August–October 1944) and Yalta (February 1945). The evidence is that the United States, Soviet Union, United Kingdom, and China all favored the principle of unanimity, not only out of desire for the major powers to act together, but also to protect their own sovereign rights and national interests. Harry S. Truman, who became President of the United States in April 1945, wrote: "All our experts, civil and military, favored it, and without such a veto no arrangement would have passed the Senate."