By mid-1943 the tide of war was turning decisively against Germany. The last major German offensive on the Eastern Front, Operation Citadel, ended in the defeat for the Germans at Kursk, and in July 1943 Mussolini was overthrown. The Army and civilian plotters became more convinced than ever that Hitler must be assassinated so that a government acceptable to the western Allies could be formed and a separate peace negotiated in time to prevent a Soviet invasion of Germany. This scenario, while more credible than some of the resistance's earlier plans, was based on a false premise: that the western Allies would be willing to break with Stalin and negotiate a separate peace with a non-Nazi German government. In fact both Churchill and Roosevelt were committed to the “unconditional surrender” formula.