Operation Sledgehammer 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 . The operation was eagerly pressed for by both the United States military and the Soviet Union , but it was never actually carried out as it was finally realized that it was wholly impractical at that period in time , an assessment which was vindicated by the Dieppe Raid of August 1942 . History . After the United States entered World War II , the U . S . Joint Chiefs of Staff pressed for an invasion of mainland Europe via the English Channel " as soon as possible " , i . e . the early part of 1942 . The British were , however , reluctant , as it was felt that other places had a higher priority , the time was not right and insufficient men and landing craft were available . The U . S . tended to regard this reluctance as an example of British caution but since at the time they lacked the resources to carry out such an operation themselves , the result was stalemate , along with increased pressure on the British , which began in March 1942 with a letter from President Roosevelt to Winston Churchill : On 8 April , General George Marshall and Harry Hopkins arrived in Britain to press the case for two possible American plans for a landing in Occupied France : Operation Roundup . Roundup was to be executed by 48 Allied divisions , 18 of which would be British . It was to be mounted before April 1943 . Operation Sledgehammer . Sledgehammer was a plan to capture the French seaports of either Brest or Cherbourg during the early autumn of 1942 in the event that Germany or the Soviet Union was at the brink of collapse . Sledgehammer was to be carried out mainly by British troops as the Americans could only supply two or three divisions in time . Churchill responded that it was " more difficult , less attractive , less immediately helpful or ultimately fruitful than Roundup " . After capturing Cherbourg and areas on the Cotentin peninsula , the beachhead was to be defended and held through the winter of 1942 and into 1943 , while troops were massed for a breakout operation to take place in spring 1943 . This plan became popular and received the codename Sledgehammer . Hopkins added additional political weight to the proposed plan by opining that if U . S . public opinion had anything to do with it , the U . S . war effort would be directed instead against Japan if an invasion of mainland Europe was not mounted soon . However , the elements required for such an operation were lacking , i . e . air superiority , amphibious warfare equipment , sufficient forces and adequate supply . Despite all this , the Joint Chiefs of Staff considered Sledgehammer feasible . If Sledgehammer had been carried out , the British could have landed only six divisions at most , whereas the Germans had 25 - 30 divisions in Western Europe . Assuming it could be established in the first place , a beachhead on the Cotentin peninsula would be blocked off and attacked by land , sea and air . Cherbourg , the only suitable port would no doubt be mined , while aircraft and artillery would be expected to attack the town in strength , while German armoured forces were brought to bear . The pressure to mount Sledgehammer increased further when Soviet Foreign Minister Vyacheslav Molotov arrived in the UK to press for a Second Front . After trying and failing to persuade Churchill , Molotov travelled on to Washington where he enjoyed a better reception and received more support for his requests . He then returned to London convinced that a Second Front in 1942 was an actual part of Anglo - American policy .