Thach had heard, from a report published in the 22 September 1941 Fleet Air Tactical Unit Intelligence Bulletin, of the Japanese Mitsubishi Zero's extraordinary maneuverability and climb rate. Before even experiencing it for himself, he began to devise tactics meant to give the slower-turning American Grumman F4F Wildcat fighters a chance in combat. While based in San Diego, he would spend every evening thinking of different tactics that could overcome the Zero's maneuverability, and would then test them in flight the following day.