Attack types
Bombardment
one-sided (i.e. damage done only to the defender)
the attacker must have weaponry with the range of a tile, which excludes most artillery and battleships, but includes missiles
Raid
two-sided (i.e. damage done to both the attacker and defender), unless the attacker significantly out-ranges the defender (e.g. a battleship conducting a raid on a port that is only defended by infantry)
naval raids can only be conducted on tiles that have ports
naval raids can result in capturing ships
the enemy tile is not captured
Offensive
two-sided
if the offensive is successful, the tile is captured, the enemy is destroyed or retreats
a naval offensive is only possible if there are troops to land, ships with ranged weaponry support the landing