Who was president of the us when the first world war began?

At the point in time when World War I, also known as the First World War, the Great War, and the War to End All Wars, the global military conflict that embroiled most of the world's great powers, assembled in two opposing alliances: the Entente and the Central Powers did the intransitive action begin (commence or get going), who satisfies: X is the president (head of a nation state) of The United States of America (also called the United States, the U.S., the USA, America, and the States), the federal constitutional republic comprising fifty states and a federal district?