On 25 July 1943, following the Allied invasion of Sicily, King Victor Emmanuel III dismissed Mussolini, placed him under arrest, and began secret negotiations with the Western Allies. An armistice was signed on 8 September 1943, and four days later Mussolini was rescued by the Germans in Operation Oak and placed in charge of a puppet state called the Italian Social Republic ("Repubblica Sociale Italiana"/RSI, or "Repubblica di Salò") in northern Italy. In order to liberate the country from the Germans and Fascists, Italy became a co-belligerent of the Allies; as result, the country descended in Civil War, with the Italian Co-Belligerent Army and the partisans, supported by the Allies, contended the Social Republic's forces and its German allies. Some areas in Northern Italy were liberated from the Germans as late as May, 1945. Mussolini was killed by Communist partisans on 28 April 1945 while trying to escape to Switzerland.