National Objectives were introduced as an option in AA50 and are an integral part of AAG40,AAE40 and AAP40. The allow players to gain income by meeting certain conditions, generally territory control.
Their purpose in AA50 was to encourage more historical strategies. The Pacific has little income, but US & Japanese objectives give more reason to fight. The Russians in AA50 receive a bonus for keeping their allies off their territory. The game still works without using the objectives. The same objective are used for the AA50-41 and AA50-42 scenarios.
In AA40, there is a different set of national objectives for each scenario.
National objectives are controversial with players. Many feel that it adds complexity for a little gain. If the designer wants players to fight over Pacific islands, just raise their income value.