In July 1943, Allied troops invaded Sicily, overthrowing Mussolini. In September 1943, Operation Avalanche landed Allied troops on the Italian mainland near Salerno. The invasion of Italy was slowed by German resistance and Italy's mountainous terrain. In January 1944, Allied troops landed at Anzio but became trapped there for four months until breakthrough in May 1944. Allied forces entered Rome in June 1944 and continued fighting until Germany surrendered in Italy in April-May 1945.