Operation Sledgehammer was a World War II Allied plan for a cross-Channel invasion of Europe, as the first step in helping to reduce pressure on the Soviet Red Army by establishing a Second Front. Essentially, Allied forces were to seize the French ports of either Brest or Cherbourg during the early autumn of 1942 along with areas of the Cotentin Peninsula, and then amass troops for a breakout the spring of 1943, and as such, was a contingency alternative to Operation Roundup, the original Allied plan for the invasion of Europe in 1943.