 The II Canadian Corps would simultaneously launch Operation Atlantic a supporting attack on the VIII Corps western flank, to capture Caen south of the Orne river.The British and Canadian operations were tentatively scheduled for 18 July and Cobra was postponed for two days, to enable the First Army to secure its start line around Saint-Lô.Detailed planning began on Friday 14 July but the next day, Montgomery issued a written directive ordering Dempsey to change the plan from a "deep break-out" to a "limited attack".