Avalon Hill’s Under Fire! (Commodore 64)
Avalon Hill's Under Fire! was the war game to have when it was released. It was a tactical World War II land combat simulator. The graphics were pretty basic but it was the game play that mattered. Based on the ads, it looks like the Apple II version was released first, followed later by ports for DOS and the Commodore 64. The ad above is from 1988 and is advertising the DOS and Commodore 64 versions as a "new conversion".
While the graphics weren't terrific on any system, they were better on the Apple II and Commodore 64 than the DOS version but that was a trade off for slightly slower game play. The main screen was a simple map divided into squares. The scale of the game or how much space each square represented was user selectable. Units were represented by simple symbols...soldier, tank and halftrack. Under Fire can be played with one or two players. Depending on the scenario, games can last from 10 minutes to many hours.
There were two "Extended Capabilities Disk" expansions that added various improvements, units, maps, and scenarios. These were both released only for the Apple II and I believe they were both released before the DOS and Commodore 64 ports. I am unsure whether these additions and improvements were incorporated into those versions or not.
Tactical turn based games like Under Fire used to be a lot more common than they are now. This is a case where many of the best games in this category are very old games. There aren't any new versions or ports of this game so you'll have to track down an original disk or use emulation.
Screen shots above are from the Commodore 64 version of the game.