Base Wars was set in the "future" in a time when team managers and owners were presumably sick of dealing with professional sports players primadonna antics—so they replaced all of them with robots, which you then get to play as. In the cut screens, these robots look like pretty tough cylon-ish creatures, but there are actually four different classes that you can play as: a tank, a "flybot," an android, and a dude with a motorcycle instead of feet.
The player is able to choose between Open Mode and Pennant mode, which are exactly what they sound like. You then have to choose between 14 different teams, most of which are represented by cities, but two of which you are able to customize and play with as well. These customizable teams are also given weapons: laser swords or laser guns. I am personally preferential to the laser swords, as I think it makes more sense when fighting up close as you so often have to do in this game.
Overall, I think that this is a pretty solid game—the graphics aren't as terrible as they could be coming from NES in 1991, and the gameplay is unique with the fighting aspect. While this could have been a pretty stale baseball game, like some other ones that I've played, the designers kept it interesting and fresh with the storyline that they introduced. If you are interested in playing this game for either nostalgia's sake or because you haven't before, you can do so here. Happy gaming!