The dual-mode Siege Tank concept was a response to the Guild Wars and the Goliath. Prior to the war work had progressed on a static "final defense" cannon. However the war demonstrated the need for mobility and as a result an effort was made to make the cannon more mobile. The solution was creative. An existing tank design was modified such it could operate as a conventional tank in addition to being able to deploy the cannon and become a static artillery emplacement at will.
In "tank mode," the Siege Tank employs twin 80mm PPG-7 plasma cannons. However, once it extends its stabilizers it can deploy the awesome 120mm Arclite Mjolnir Artillery Cannon, transforming the tank into an effective long-range artillery support platform. The tank has a crew of three: gunner, driver, and commander/navigator.
In tank mode the Siege Tank is decent against "Large" ground units. Arguably, it's still not as efficient as a group of Marines, especially if a force is being moved by Dropship (which can carry 2 tanks or 8 marines).
With siege mode the Siege Tank comes into its own. Very long range and high damage make it eminently useful for defense (supporting bunkers) or offense (using two groups of tanks to leapfrog forward). The temporary loss of mobility is a small matter. The Shock Cannon has longer range than the tank's own sight range, so using another unit as a spotter gets the most out of siege mode.
The Shock Cannon causes splash damage to all units and has a minimum range. Therefore tanks in siege mode need other units to guard it (perhaps even other tanks in siege mode), although these guards might take damage from the shock cannon as well as the enemy. The guards can also screen for the tanks as they withdraw. Transforming between modes takes time, during which the tank is unable to move or attack.
Some players prefer to "wall-in" their Siege Tanks, by erecting buildings to surround the tank, thereby preventing the enemy from getting closer than the minimum range of the shock cannon.
- Siege Tech
The Siege Tank has many stereotypical, military quotes. The driver of the tank is seen as a large man in body armor who speaks in army lingo. Several of his quotes are obviously taken from the classic Vietnam War films Full Metal Jacket and Apocalypse Now.
In StarCraft: Ghost, Nova was able to call down artillery support from Siege Tanks by identifying targets. The Shock Cannon fired blue plasma rounds in campaign, but green in multiplayer. Siege Tanks were player drivable in multiplayer, and were able to run over and crush other players and vehicles. 
The Siege Tank in StarCraft II still deploys into artillery mode, the only difference being its physical appearance.
Siege tanks cannot fire when moving, leaving the tank vulnerable to attacks by melee units.
Known Siege Tank Commanders
The Mjolnir cannon is a reference to the hammer of the Norse god of thunder, Thor.
- ↑ 1.0 1.1 1.2 Underwood, Peter, Bill Roper, Chris Metzen and Jeffrey Vaughn. StarCraft (Manual). Irvine, Calif.: Blizzard Entertainment, 1998.
- ↑ Goldstein, Hilary. 2003-03-31. Starcraft: Ghost Details. IGN. Accessed 2007-09-01.
- ↑ Source: BlizzCon 2005 StarCraft: Ghost information. Terran Vehicles. Artist: Blizzard Entertainment. Accessed 2007-09-08.
- ↑ Karune. 2007-10-10. Karune: Tanks, Shoot While Moving? Battle.net StarCraft II General Discussion forum. Accessed 2007-10-10.
- Arclite Siege Tank Battle.net StarCraft Compendium's official strategy page about Siege Tanks.