On August 19, 1942, Allied troops conducted a raid on the German-occupied port of Dieppe, France. Codenamed Operation Jubilee, the intent of the Dieppe Raid was to prove that the Western Allies were able to take and hold territory in occupied Europe while also destroying German defenses, gathering intelligence, and boosting morale. To achieve these objectives, approximately 5,000 Canadian infantrymen, 1,000 British commandos, 15 Free French commandos, and 50 US Army Rangers (marking the combat debut of American forces in Europe during the war) were assigned to land and take the port with support from the Royal Navy and Royal Air Force.
Unfortunately, the raid was a complete disaster. Within 24 hours over 60% of the raiding force had been killed, wounded, or captured. At least 100 RAF aircraft as well as a RN destroyer and ~30 landing craft were also lost, plus numerous tanks and vehicles fielded by the invasion force. Strong German defenses combined with problems in coordination (notably the delay in arrival of armor for the main Canadian force, compelling them to advance without armored support under heavy German fire) and inadequate preparation resulted in the raid's failure.
However, the raid did show the Allied command that they had serious issues which needed to be addressed before conducting another amphibious invasion. Lessons learned from the disaster at Dieppe would be applied in the future landings in North African, Italy, and France.