The doctrine that socialism ought to come by international revolution. Marx and Engels called for ‘Workers of all countries’ to ‘unite!’ in 1848. The International Working Men's Association (First International) was founded by Marx in 1864 and dissolved in 1876 when he moved its headquarters to New York in order to prevent it falling into the hands of his opponents. The Second International was founded in 1889. It embraced both Marxists and non‐Marxist socialists, but fell apart in 1914 when the majority of the socialists in all the combatant countries in the First World War embraced their country's war effort. The Third (communist) International was founded in 1919 and dissolved in 1943. Official doctrine in the Soviet Union promoted international socialism at some times, and socialism in one country at others, according to the perceived needs of the USSR. Trotskyists founded a rival ‘Fourth International’. Groups calling themselves International Socialists in capitals are therefore Trotskyist.