The game was called Circumvallation. The tagline on the box read: "Uncle Toby's favourite game!" (perhaps a reference to Tristam Shandy). The setting of the game appeared to be the Thirty Years War. But the point of the game was to conquer a fortified town. One player is the besieger and the other is the besieged. Each team gets various military units and defenses. Furthermore, they can deploy additional resources as the game proceeds.
Essentially, the besieger has twenty turns to take the town, at which point an ally comes to save the town. But they also can't run out of food. And I think there were add on packs for specific historical events like the Siege of Breda or the Siege of Haarlem.