Jean Jaurès (; full name Auguste Marie Joseph Jean Léon Jaurès; 3 September 185931 July 1914) was a French Socialist leader. Initially an Opportunist Republican, he evolved into one of the first social democrats, becoming the leader, in 1902, of the French Socialist Party, which opposed Jules Guesde's revolutionary Socialist Party of France. The two parties merged in 1905 in the French Section of the Workers' International (SFIO). An antimilitarist, Jaurès was assassinated at the outbreak of World War I, and remains one of the main historical figures of the French Left.