At the end of August 1944, the majority of German military units in Greece began withdrawing because of the Soviet Union's offensive into Romania and the latter changing sides. This was followed shortly after by Bulgaria entering the war against Germany and the Yugoslav Partisans attacking German lines of communication. With German formations remaining only on a handful of Greek islands, the British moved forward with their plan to reoccupy the country. On 18 October, supported by British forces, the Greek government-in-exile returned to Athens; this was part of a larger geopolitical move to install a British-friendly, non-communist government in Greece. During the occupation, Britain had provided military support to the National Liberation Front (EAM), a combination of five socialist and communist parties, which controlled the large Greek People's Liberation Army (ELAS). In early 1944, the Greek Civil War broke out between the EAM's forces and the non-communist partisan movements, such as the National Republican Greek League (EDES). After the re-establishment of the Government of Greece, tensions rose, culminating with the EAM attempting to seize power in December and the British military becoming involved within the second phase of the Greek Civil War.