In 1943, the British Special Operations Executive (SOE) launched one of the Allied intelligence services' biggest efforts to foster resistance within Nazi Germany in cooperation with Slovene partisans in the Carinthian borderland. The so-called Clowder Mission systematically supplied weapons and other military assistance to the partisans who, in summer and autumn 1944, offered the strongest – albeit often neglected by scholars – militant resistance within the borders of Nazi Germany. Although SOE's operational aim of externally fomenting Austrian separatist, patriotic resistance deeper inside the country failed, its strategic aim of assisting the separation of Austria from Germany and re-establishing an independent Austrian nation-state proved to be sound. At the same time, the Carinthian Slovene partisans fell short of attaining their political objectives. This article analyses the paradoxical results of British subversive politics towards Austria and Slovenia. It traces the impact of the SOE's agenda and the origins of the Moscow Declaration on the reestablishment of Austria, and elaborates on the character of British-Slovene cooperation, its success and its breakdown in the context of British subversive politics, inter-Allied rivalries and competition, and the geopolitics of resistance.