This was a British and Canadian exercise in the Chiltern Hills of southern England (September/October 1941).
The object of the exercise was to test current British capability to defeat a German invasion of East Anglia, and pitted two corps and one armoured division of Lieutenant General the Hon. Sir Harold Alexander’s Southern Command against two corps and one armoured division of Lieutenant General L. Carr’s Eastern Command. Air support was provided by Air Vice Marshal D. F. Stevenson’s No. 2 Group of Air Marshal Sir Richard Peirse’s RAF Bomber Command and also by Air Marshal Sir Arthur Barrett’s RAF Army Co-Operation Command, the outcome being a narrow 'victory' for Alexander.