fun game with a lot going on. if you're struggling:
1) pick any race (preferably one that has normal or better spearmen)
2) upgrade spear training / armor only
3) pick one lane, send spearman in that lane only (generally ur units will stack and win lel)
4) if u fail, just try again, save gold only for spearman upgrade.
5) eventually destroy entire map
optional:
6) can cheese easy mission by surrender before win to stockpile gold.
7) can add difficulty by upgrading different unit type.
to defeat iowa: get all artillery battery and build the fortress, and fill it with artillery and torpedo turrets. bide time, gain cash, use a light-medium assault of cruisers and destroyers to provoke an attack. be sure to focus fire on battleships first. send subs/frigates/cruisers and defeat the attack, rebuild fortress if it was destroyed. weaken the enemy base to below 1000 hp, iowa comes out, focus fire all batteries on iowa, send mass subs/cruisers and the odd bomber to cheese iowa. Its important you get a wall of cruisers to stop the enemy bombers...or all of your stacked ships/subs die in 2-3 bombs. atomic sub is a good meat shield, but please do not rely on it, as it does not deal nearly enough damage for its cost, better to save for a bomber plus 2-3 jets once you have taken out their air defense.