Stellar Crusade is a two-player turn-based strategy game set in space, written by Norm Koger and published by Strategic Simulations, Inc. in 1988.
Two ideologically opposed powers compete to colonize and then conquer a star cluster in the 24th century. This is an excellent one-on-one game, and an early example of a 4X. You could see the map, but until you sent a ship to a system you couldn't be sure what resources it had.
Stellar Crusade is ultimately about conquest; the two sides are itching for war from the outset, and the battle starts as soon as they can reasonably reach each other. The game is split between economics (building your military/industrial complex) and combat.
It's an excellent game, though the graphics haven't aged well. If you can get past the late '80s visuals, it's a classic and remains fun.
Places to Buy
Look for Stellar Crusade on your favorite abandonware site.