On 18 June, Montgomery issued a directive to Dempsey to launch a new pincer attack with the aim of capturing Caen. The initial plan called for I and XXX Corps to attack west of Caen for four days, before VIII Corps launched the main attack out of the Orne bridgehead, east of Caen, on 22 June. It was soon realised that VIII Corps would not be able to assemble within the small perimeter of the Orne bridgehead and the following day the plan was revised. A preliminary operation was to take place three days before the main assault. The 51st (Highland) Infantry Division (I Corps) was ordered to strike south from the Orne bridgehead, to prevent units of the 21st Panzer Division from being transferred. Operation Martlet was to commence one day before Epsom with the 49th (West Riding) Infantry Division and the 8th Armoured Brigade (XXX Corps) securing the right flank of VIII Corps, by capturing the high ground to the south-west.