The original version of Laser Squad, the predecessor to UFO: Enemy Unknown, developed by Julian Gollop.
5509 My guys can't get through the door I spawned them behind...
5510 Hmm... You need to equip weapons as well...
5511 I killed some robots! 'Opportunity Fire' is like Overwatch, and is automatic. You just need to save some Action Points for the enemy's turn.
5512 VICTORY TO> ASSASSIN SQUAD. I beat the first mission (level 1), 100 to 40 victory points.
5514 Beat the second mission (level 1).
5517 I couldn't figure out how to swap tapes in Speccy, but I did find laser-squad.co.uk, a site with information about the game, and downloads for separate save states for each mission, with which I can ignore tape loading completely. After a bit of URL-hacking, I even got the 6. and 7. mission downloaded.