Your run begins once you select a New Game (Not Continue) on the Campaign Mode (Normal game only, not hard) and ends once you destroy all enemy units or capture the Final Battle map thus finishing the game. You can continue after a defeat and go to bonus maps but of course that can affect your overall time. You can change options to quicken battle speeds but you can not reload saves.

Game Boy Advance - Advance Wars - Fastest Completion - 04:10:52.0 - Ryan Genno