Modem Wars

Modem Wars is a 1988 real-time tactical war game developed by Ozark Softscape and published by Electronic Arts for the IBM PC and Commodore 64 platforms.

Modem Wars was played over a modem connection between two machines (via telephone or null modem serial connection), with both players controlling a group of robotic units trying to eliminate the opponent's mobile Command Center (COMCEN). Features such as fog of war, varied unit types, terrain, and formations were implemented.

The game was originally developed under the title "Sport of War"; Computer Gaming World noted this was the easiest way to understand the game, saying "You play the game as a wargame, but you accumulate points as if it were a sports game." The name was changed to Modem Wars to call attention to how the game is intended to be played against other humans via modem. The computer AI opponent is referred to as a "solo trainer", and CGW recommended against buying the game for those planning to only play against the computer.

Of specific technical interest, Modem Wars has been lauded for its mechanism of using 4-byte packets for each 'move', deltas to determine game states, and storage of those deltas to allow for after-game replays.

Source: Wikipedia, "Modem Wars", available under the CC-BY-SA License.