Siege Mode
Source: Machine Shop
Minerals: 150
Vespene Gas: 150
Research Time: 80
Siege Mode is a must ability for any Terran player. When the tank enters Siege Mode, its range of fire will be greatly increased to highest in the game. Entering or canceling Siege Mode does take a few seconds to set up, so it is best to do so when they are not in combat. While in Siege Mode, the tank is immobile and has a minimum attack range, making them vulnerable to enemies that get to close. For these reasons, it is important to have support units to help the tanks when melee units start to attack them. The best place to use Siege Mode is on higher ground terrain to prevent melee units from getting to close.
Tanks are often put next to Bunkers when defending and accompanied by infantry when attacking. However their fire power is unmatched and it deals splash damage as well making it very effective against tightly packed mobs. A dozen or so Siege Tanks in Siege Mode placed at a strategic choke point will mow down any ground force that dares to pass. Their splash damage also affects friendly units as well and more often than not Siege Tanks will kill their allies or sometimes buildings by attacking units that are to close. Siege Mode is great for assaulting bases because they take out defensive structures, such as Bunkers and Photon Cannons, without the fear of counter attacks. When assaulting, the tanks are often put in Siege Mode while the support units stay next to tanks only attacking units that get to close. Once the tanks reduce everything to rubble, they move up a little more and repeat the process until the base is destroyed.