'Harlequin' was an Allied component of 'Cockade' to provide diversionary action against the German forces in occupied France (August/September 1943).

'Harlequin' was planned as an amphibious training exercise in the English Channel 'to try out the procedure and machinery for passing troops from Concentration Areas through Assembly and Transit Areas to embarkation hards and ports'. As such the exercise represented an embarkation programme for the invasion of France extending from D-Day to D+3. Two corps were involved, namely 2.5 divisions of Lieutenant General N. M. Ritchie’s British XII Corps passing through assembly areas in the Dover and Newhaven sectors, and 2.5 divisions of Lieutenant General G. G. Simonds’s Canadian II Corps through areas in the Portsmouth and Southampton sectors.

On reaching the waterside, most of the force turned back and dispersed, but a number of British anti-aircraft units embarked and proceeded into the English Channel as the exercise was combined with the 'Starkey' deception scheme designed to convince the Germans that an invasion was intended, and thus to precipitate a major air battle.