This checkers-type naval wargame covering the Atlantic Ocean theater was published in 1941 as simply Game of Defense. After the Japanese attack on Pearl Harbor late that year, an Atlantic sticker was added to the box, and a companion board covering the Pacific Ocean was published, using the same parts box but with a Pacific sticker added. The Atlantic map is a red-and-white checkerboard with green land areas drawn on the eastern and western edges. Five ports are circled on each side: Scapa Flow, Brest, Lisbon, Gibraltar and Dakar on the Europe/Africa side, and Halifax, New York, Charleston, New Orleans and Panama on the Americas side. Each side gets four each of three types of ship: battleships move 1-4 squares only on red; cruisers move 1-3 squares on white; and submarines move a single square without restriction. Battleships and cruisers destroy opposing ships by jumping over them (and can jump over a square of opposite color to do so), while submarines kill by moving onto another ship. At the beginning of the game, each player draws one of five Objective cards naming a port on the opposite side, and also writes down 10 numbered squares (of 50 on the board off both coasts) as secret minefields. Players move alternately, either a single ship or up to 5 ships on adjoining squares as a fleet move. If a ship moves onto or over a minefield, a card is drawn from the deck showing the consequences. The winner is the first to have the stated number of ships reach shore at that player's Objective.