Yeah, Adrien has it right. If you were allowed to change production after your opponent played everyone would want to play second in a war split.
Played: Pitboss 18 - Kublai Khan of Germany Somalia | Pitboss 11 - De Gaulle of Byzantium | Pitboss 8 - Churchill of Portugal | PB7 - Mao of Native America | PBEM29 Greens - Mao of Babylon