By the spring of 1942, both the Soviet premier, Joseph Stalin, and the American president, Franklin D. Roosevelt, wanted an Anglo-American force to establish a "second front" in western Europe. However, neither the British nor Americans had any practical experience in conducting large-scale amphibious operations. Landing craft were in short supply and not enough were available to support a full invasion of the continent. The British prime minister, Winston Churchill, proposed that an amphibious "raid" be conducted upon the French port of Dieppe to placate the Soviets.
The raid was to be carried out by 5,000 troops from the 2nd Canadian Division, supported by 1,000 British Commandos and 90 American Rangers. Although no preliminary air or naval bombardment of Dieppe was to be provided, Royal Air Force (RAF) squadrons, including eight from the RCAF, would provide air cover. Artillery FOOs (Forward Observation Officers) called down naval gunfire to support the assaulting troops. Ground attack aircraft provided similar support. The RAF had flown several reconnaissance missions over Dieppe, but they had failed to spot the German machine gun and artillery emplacements that had been constructed in the cliffs on either side of Dieppe harbour. In addition, the slippery shale beaches of Dieppe were not suitable for the deployment of tanks.
Various units of the 2nd Canadian Division were involved in the operation. The Cameron Highlanders of Winnipeg and The South Saskatchewan Regiment landed at Pourville to the west of Dieppe, while The Royal Regiment of Canada from Toronto, with a company of Montreal's The Black Watch (Royal Highland Regiment) of Canada, landed to the east at Puys. Les Fusiliers Mont-Royal, The Royal Hamilton Light Infantry, The Essex Scottish Regiment from Windsor, and the 14th Army Tank Regiment (The Calgary Regiment), equipped with the new Churchill tanks, made the assault on the main beaches at Dieppe. The tank engagement was the first operation involving the Canadian Armoured Corps, which had been formed in 1940. The 14th Tank Regiment was converted from infantry to tanks in the 1936 restructuring of the militia.
A British officer, Lieutenant-General Bernard Montgomery, was to command the operation, and Canadian Major-General J.H. Roberts would command the landing forces. The Combined Operations Headquarters had planned to launch the raid in the first week of July but had postponed the operation due to bad weather. The raiding force returned to barracks. These soldiers had been issued special weapons for the raid, and many of these arms required careful individual adjustments and modifications to ensure they worked smoothly. When the raid was rescheduled, the troops were again issued special weapons that were taken straight out of stores. On this occasion, they had no chance to properly adapt and test them, and, at that point, Lieutenant-General Montgomery recommended that the raid be cancelled. Combined Operations Headquarters, however, insisted that the Dieppe operation was essential for planning the future invasion of France. On 13 August 1942, Lieutenant-General Montgomery was appointed commander of the British 8th Army in North Africa. General Paget, the British Commander-in-Chief, Home Forces, and Lieutenant-General Andrew McNaughton, the Canadian General Officer Commanding, assumed overall responsibility for the Dieppe operation. Major-General Roberts retained command of the assault forces. The Dieppe raid was now to be conducted on 19 August 1942. The prevailing opinion of Combined Operations Headquarters was that the element of surprise would be sufficient to guarantee the success of the operation.
On the night of 18 August, a small fleet of 250 vessels began to transport the Dieppe force. At 3:47 a.m., 19 August, the landing craft encountered a small German convoy lighting up the sky and alerting German troops along the French coast. When the 2nd Canadian Division began landing on the Dieppe beaches at 5:20 a.m., the Germans met them with a hail of machine gun and artillery fire from the emplacements in the cliffs on either side of the harbour. When the tanks of The Calgary Tank Regiment arrived, they bogged down on the slippery shale beach and were easy targets for German anti-tank crews.
The raid was a complete disaster. Major-General Roberts attempted to evacuate the force, but he only managed to retrieve 2,221 Canadian officers and men. The 2nd Canadian Division had lost 3,367 men: 946 were killed and the remainder became prisoners-of-war. Major-General Roberts himself became a casualty as he was removed from command of the 2nd Division and given a minor command position. Most historians now tend to view this decision as unjustified: responsibility for the failure resided at a much higher level than his position of tactical command.
However, the Allied High Command had learned that the success of any future amphibious operations would require heavy preparatory fire support from naval and air force units. Many other lessons were learned that made a direct impact on the success of the D-Day landings in Normandy two years later. Above all, the Dieppe raid impressed on political and military leaders and planning staffs just how difficult an amphibious invasion was going to be.