Star Fleet II: Krellan Commander, published in 1989, was an ambitious game of space combat strategy, with the player this time controlling the invaders forces (the Krellans) as they invade UGA territories. The game had planetary bombardment, invasions, ship-to-ship beam-over boarding parties, and so much more. It is a fun (if complex) game that, in its initial 1.0 version, had bugs that prevented sections of the game from functioning. However, Dr. Trevor Sorensen released a revised versioon of the game (v1.5 and later 1.5b) to make the game fully playable.
If you would like to play Star Fleet II: Krellan Commander but do not have access to a working copy of the latest release, click here to download StarFleet II: Krellan Commander version 1.5Bb, which corrects many of the bugs in the earlier version 1.0 and 1.5 (no letter indicating subversion). Click here to download the Star Fleet II Officer's Manual.
The Moby Games site has a nice collection of screen shots from Star Fleet II: Krelan Commander.