Operation Sledgehammer was an Allied plan for a cross-Channel invasion of Europe during World War II, as the first step in helping to reduce pressure on the Soviet Red Army by establishing a Second Front.
Allied forces were to seize the French Atlantic ports of either Brest or Cherbourg and areas of the Cotentin Peninsula during the early autumn of 1942, and amass troops for a breakout in the spring of 1943.
In March 1942, in a letter to British Prime Minister Winston Churchill, U.S. President Franklin Roosevelt wrote: I am becoming more and more interested in the establishment of a new front this summer on the European continent, certainly for air and raids.
Hopkins added additional political weight to the proposed plan by opining that if US public opinion had anything to do with it, the war effort would be directed instead against Japan if an invasion of mainland Europe was not mounted soon.
[4][5] At the Second Washington Conference in June 1942, President Roosevelt and Prime Minister Churchill decided to postpone the cross-English Channel invasion until 1943 and make the first priority the opening a second front in North Africa.
At the Second Claridge Conference in London, July 20–26, Churchill and Roosevelt aid Harry Hopkins agreed to substitute Operation Torch, the invasion of French North Africa, for US reinforcement of the Western Desert campaign.
[6] Senior U.S. commanders expressed strong opposition to the landings and after the western Allied Combined Chiefs of Staff (CCS) met in London on 30 July, General Marshall and Admiral Ernest King declined to approve the plan.