Archival documents from Russia, which are becoming more accessible, help to provide a more accurate accounts of Iran's political past. Based on Soviet documents from the Russian State Archive of Socio-Political History, as well additional primary and secondary sources in various languages, the focus of this article is on the challenges and obstacles which the Tudeh Party faced from the British and their proxies in Iran during the Allied occupation of Iran in Second World War (thus creating Tudeh's ‘British Problem’). The article delves not only on describing and analyzing those challenges and obstacles, but also on the way the Tudeh was able to overcome them, and its political breakthrough and success in the Fourteenth Majlis elections and later in introducing three of its members into Qavam's coalition government. Faced with such successes of the Tudeh, and worried about the future of their own interests in Iran, and especially the oil installations of the AIOC, the British sought American assistance. According to the Soviet view, it was only through an Anglo-American cooperation that Tudeh's political rise in Iran was checked.