Complex sentence: The International Socialist Organization (ISO) is a revolutionary socialist organization in the United States that identifies with the politics of International Socialism, a form of Trotskyism, and the Marxist political tradition that American Trotskyist writer and activist Hal Draper called "socialism from below".
Split into simpler sentences: The International Socialist Organization (ISO) is a revolutionary socialist organization in the United States. The group identifies with the politics of International Socialism, a form of Trotskyism, and the Marxist political tradition that American Trotskyist writer and activist Hal Draper called "socialism from below".