Between 1918 and 1923, Istanbul was the capital of a defeated empire and occupied by the “interallied” forces composed of Britain, France, and Italy. Notwithstanding, or precisely due to, these conditions, it functioned as a vibrant hub of global communist militancy. This article explores the brief history of occupied Istanbul and discusses different agents and aspects of communist network-making. It underlines the agency of two neglected actors: a multinational body of communist sailors who connected Istanbul and its communists to European, Middle Eastern, and Soviet ports; and European and colonial soldiers stationed in Istanbul, who counterintuitively contributed to these connections. Finally, it shows how Istanbul, as the multiethnic and multilinguistic soon-to-be-former capital of the Ottoman Empire, provided a fertile ground for communist connections.