Many former professional and top-level association footballers lost their lives during World War II, either while serving in their own or other countries' armed forces, as civilian casualties of enemy action or in enemy captivity. In addition, a number of Jewish players became victims of the Nazi Holocaust. In the case of players whose countries were annexed by others or who migrated from their country of birth, they are classified under the nation of football association in which they spent most if not all of their playing careers.