In this mission there is a nearly symmetrical map with you on the left and the enemy (Blue) on the right. Blue has a slight advantage in units (an extra tank and sub), slightly more starting cash, and also a significant advantage in resource (oil) production: Blue starts with the equivalent of 12 refineries and can easily increase to 14 unopposed, whereas you start with the equivalent of only 4 refineries and can only grab another 3 without serious opposition. So in effect Blue has twice your resource income each turn. Correcting this resource gap is critical, otherwise you will be ground down in a war of attrition.