The aim of my paper is to examine how the Turkish resistance movement emerged in Istanbul, the capital city of the Ottoman Empire, which came under Allied occupation following the First World War. The formation of this movement will be analyzed in the broader context of Turco-Soviet relations after the Bolshevik Revolution in Russia. More specifically, I will examine the development of a rapprochement between the Bolsheviks and the Unionists, i.e. the members of the Committee of Union and Progress (CUP) that had ruled the Ottoman Empire in an authoritarian manner during the First World War. Although the CUP was formally abolished in November 1918, the Unionists maintained the integrity of the organization while laying the foundations of a national resistance against the partition of the Ottoman Empire. Meanwhile they saw the Bolshevik Russia as a potential ally. There is a considerable literature on the rise of a Bolshevik-Unionist alliance and its strategic results for the Greek-Turkish military confrontation in Anatolia (1919-1922). Yet the consequences of this process for the occupied Istanbul form a subject that has not been thoroughly researched. My paper will address this topic by focusing on the efforts of the Unionist leaders in Istanbul to draw on the support of the Bolsheviks in their struggle against the British, French, and Italian occupation. One of the most important findings of my research is that the development of the Bolshevik-Unionist relations enabled the nascent Turkish communist movement to take initiative in the formation of an underground resistance in Istanbul soon after the Allied powers established military control over the city in March 1920. Most active in this process were the agents dispatched by the Turkish Communist Organization (TCO) to the Ottoman capital. The TCO had been founded in Russia under the patronage of the Bolshevik Party and its headquarters had been moved from Odessa to Baku in May 1920.