Poland, 1939: The First Battle (1973)

This is a wargame set during the German invasion of Poland in 1939. In addition to the historical scenario, it has a number of hypothetical changes that can be made to each side's forces. The game is primarily for two players, but it is possible to play with a third player controlling the Soviet forces. The game was originally published in 1973, with a revised version published in 1974 and a further revision published in 1976.