This is XBattle by Greg Lesher, based on the original by teve Lehar released
in 1991, and including certain enhancements, modifications, and bug fixes
suggested by a number of contributers from all over the world.

XBattle is a concurrent multi-player game which combines elements of strategy
with arcade-like action to capture a wide range of military scenarios.
The game is based on X Windows, which you must have installed to run xbattle.
Opponents play from separate displays, with commands being executed concurrently
-- the players do not take "turns", but rather they all issue their commands
simultaneously. There can be any number of players, with each player assigned
to a specific team, indicated by marker colors. The game board is a matrix
of cells (square, hexes, etc.) that can be occupied by colored troops,
with the goal of the game being to eliminate the enemy from the board by
attacking cells occupied by enemy troops. A wide variety of command line options
(and previously configured game files) provide an abundance of different
scenarios and gaming environments.

If you have never used xbattle before, read the introduction on the xbattle Web
site. To get the feel of the game, you can run the "tutorial1" and "tutorial2"
scripts supplied with the game. These start a series of small example games that
you can play around with to learn the various options available with the game.

Wikipedia Xbattle

WWW: https://web.archive.org/web/20011128105604/http://cns-web.bu.edu/pub/xpip/html/xbattle.html