- Terran Siege Tank(src)
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 so that it could operate as a conventional tank in addition to being able to deploy the cannon and become a static artillery emplacement at will.
Siege tanks function in two modes. First is the "tank" or "assault mode" whereas the vehicle may be used in the familiar armored support role using relative light weapons. The second is the more radical "siege mode" whereas the vehicle becomes a static emplacement able to deploy a much more powerful and longer ranged weapon.
The AAV-5 was in service by the late 2490's, renowned throughout the Confederacy for its heavy firepower and stalwart emplacement/advance tactics. It had a crew of three: gunner, driver, and commander/navigator, though could still be crewed by a single operator In addition, the Arclite version could serve as an APC of sorts, carrying personel into a hot zone and deploying them via side/rear hatches.
The Arclite made navigation easy via its interior viewscreen, although a top hatch still existed should a crewmember wish to survey the area personally and/or signal fellow soldiers. The tank also provided a targetting computer, which not only keyed in on heat sources, but also identified their range, notably whether they were in range or not.
Arclite armament consisted of twin 80mm PPG-7 plasma cannons when mobile and the 120mm Shock Cannon when in siege mode. Later on this was upgraded to the 120mm Mjolnir Artillery Cannon, which fired plasma shells in contrast to the standard explosives of the Shock Cannon..
Experience found the AAV-5's protection and "assault mode" armament to be inadequate. This inhibited its ability to advance and establish a "siege mode" fire base. Furthermore, once in "siege mode" it became difficult to repel a close-assault by any enemy forces taking advantage of the "deadzone" formed by its artillery cannon. As such, it has been replaced by the Crucio variant (see below).
The Crucio was designed to correct the perceived deficiencies of the AAV-5 and entered Dominion service as the AAV-5's replacement following the Brood War. The new turret layout features an upgraded assault-mode armament package so that the Crucio can fend for itself more successfully in an open battlefield. Force deployment costs for the Crucio have increased over the older Arclite, but the increased versatility of the powerful new siege tank more than compensates for the additional expense. The Crucio features twin 90mm cannons and has retained the 120mm Shock Cannon.
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 continues to function as it did in previous games with the dual tank and artillery modes. The tank cannot fire when moving, leaving the tank vulnerable to attacks by melee units.
The Siege Tank in StarCraft II represents the Crucio type.
Known Siege Tank Commanders and Crewmen
- Edmund Duke (formerly an officer of the Terran Confederacy)
- General Martin (mercenary leader)
- Sergeant Forest Keel
- Private Armstrong
- The Mjolnir cannon is a reference to the hammer of the Norse god of thunder, Thor.
- Crucio is a Latin word which means "to torture."
- ↑ 1.0 1.1 1.2 1.3 1.4 Underwood, Peter, Bill Roper, Chris Metzen and Jeffrey Vaughn. StarCraft (Manual). Irvine, Calif.: Blizzard Entertainment, 1998.
- ↑ 2.0 2.1 Arclite Siege Tank. StarCraft Compendium. Accessed on 2008-01-09
- ↑ 3.0 3.1 3.2 3.3 Neilson, Micky. StarCraft: Uprising. New York and Toronto, Ontario: Pocket Books, December 2000. ISBN 0-7434-1898-0 (eBook only).
- ↑ 4.0 4.1 4.2 Source: BlizzCon 2005 StarCraft: Ghost information. Terran Vehicles. Artist: Blizzard Entertainment. Accessed 2007-09-08.
- ↑ 5.0 5.1 Crucio Siege Tank. Blizzard Entertainment. Accessed 2008-01-08.
- ↑ 2001-01-31. StarCraft: Brood War. Vivendi Games. Mission: Mercenaries II (in English). Map Archives: Mercenaries II.
- ↑ Goldstein, Hilary. 2003-03-31. Starcraft: Ghost Details. IGN. Accessed 2007-09-01.
- ↑ Karune. 2007-10-10. Karune: Tanks, Shoot While Moving? Battle.net StarCraft II General Discussion forum. Accessed 2007-10-10.