The Yamato cannon is mounted on the prow of battlecruisers, and draws power from their core. It generates a dense magnetic field to harness a controlled nuclear reaction, turning it into a concentrated energy blast that can destroy almost anything with a few shots. The cannon requires a huge energy reserve to fire, but the effects make it worthwhile. The cannon is suitable for "scorched earth" work.
By the Great War, recent research had led to the development of the weapon. In 2499, terran engineers were working overtime to retrofit existing battlecruisers with the weapon. Behemoth-class battlecruisers received such retrofits. This trend continued with the Behemoth-class ships present within the Dominion Fleet. Some of the older vessels were not upgraded due to costs and limited supply.
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Yamato cannons possess a generator and fire control station that is manned by nearly 100 gunnery specialists.
In both StarCraft and StarCraft II, the Yamato cannon's range of ten makes it an effective siege weapon, able to destroy stationary defenses and anti-air units out of their range, leaving the battlecruiser safe. However, it takes a few seconds to charge before firing once a target is acquired. Only the strongest units can survive a shot from a Yamato cannon. The Yamato cannon is best used to eliminate strong anti-air defenders, such as enemy battlecruisers, carriers, and void rays.
Analogous to StarCraft's "Yamato Gun". Adds a large central gun to the bow. Prior to firing, the "head" splits apart, and the 'neck' recoils when the weapon is fired. Does 300 damage to any target they hit.
The Yamato gun is a possible reference to the title ship of Space Battleship Yamato and its wave motion gun and, indirectly, a reference to the Yamato-class battleship used in World War II, which were the biggest battleships ever created in their time and had the largest cannons ever to be used on a battleship.