P-52 Sea Battle

From MobyGames:
'P-52 Sea Battle is an arcade naval battle game with four types of targets: Destroyer, Torpedo (Submarines), Aircraft (Carrier), and Cruiser. Choosing either a British, American, or USSR sub, the goal is to destroy all the given targets without running out of torpedoes or being sunk.'

There is no ending after completing all 48 missions, and yes, the star means difficulty (enemies require more hits to be destroyed and can do more damage), which encourages upgrading your health points and rockets where possible. It also has a third item that looks like an emblem with a cross, this replenishes all your health though it is expensive and can only be used once per unit.

00:00 - Start
00:16 - Great Britain (1 star difficulty)
02:50 - Great Britain (2 stars difficulty)
06:46 - Great Britain (3 stars difficulty)
10:24 - Great Britain (4 stars difficulty)
14:42 - U.S.A. (1 star difficulty)
16:20 - U.S.A. (2 stars difficulty)
18:40 - U.S.A. (3 stars difficulty)
22:08 - U.S.A. (4 stars difficulty)
25:35 - USSR (1 star difficulty)
27:19 - USSR (2 stars difficulty)
29:28 - USSR (3 stars difficulty)
33:00 - USSR (4 stars difficulty)