Also…
All units are expendable, if the expenditure accomplishes something. Most units will be expended, but the challenge is to have them go in a way that they gave their money’s worth. Another important aspect of the game, which should be apparrent to a veteran player, or one with intelligence, is shielding of units. Some units (the more expensive ones) need to be protected by the less expensive ones. Infantry need to take hits for tanks, Destroyers and Cruisers should take hits for carriers… etc. Being able to scrape your expensive and better units out of a fight is essential for continuing operations and saving money. Make your enemy bleed more than you do.