The history of cannons in warfare is long and varied, starting with the first examples used during the Song Dynasty in China right up to the remarkably powerful and accurate cannons still currently utilized by military forces. The scene, which is set somewhere in the middle of that long and violent history on a battlefield far, far away, is a desperate rear guard action where the soldiers operating a lone cannon have been charged with defending their base at the far left of the screen from the big guns of the attackers who hove into view from the right; that can either be done with well placed shots knocking down incoming cannonballs or the cannons themselves.
The cannons used by both sides have a limited range, with their rounds only travelling about two thirds of the distance between the two lines, so the men operating them must rush forwards, let loose a round and leg it for cover again. The player doesn't just have impacts on their cannon to worry about either because the base behind them is also a valid target for a speeding ball of lead; three cannons are issued at the start of a game, with one being lost each time either the cannon or base take a direct hit.
IF ANYBODY CAN, CANNON CAN
The idea is simple enough to be fun, but Cannon War hasn't turned out as a particularly enjoyable game due to the implementation; being written in BASIC means that the controls can be painfully unresponsive and the action stops entirely when the player's projectile is in flight or an enemy cannon advances or retreats across the battlefield.
Had Cannon War been more responsive to the player and indeed more consistent with the overall movement and speed (if the main game had been programmed in machine code, essentially) it probably would have been a simple but reasonably fun little shooter; as it stands though, the sluggish controls and bizarre way that everything stops for tea all serve to make the game itself a frustrating experience. And yes, I've been using every ounce of willpower to resist the urge to use a phrase along the lines of "load of balls" for the last two paragraphs... oh bugger!