In the fall of 1954, Anderson-Thomson was notified that the Department of National Defence would be putting on a refereed exercise, in which the rangers were to set up a defence and secure a drop zone that was free of enemies, so that Princess Patricia's paratroopers could land. Anderson-Thomson helped the No.7 Company Rangers to build machine gun nests around the airport, as well as a maze of snowshoe trails that would lead the enemy troops to carefully placed machine gun nests. The Van Doos expected these traps, but not Yellowknife's own air force.