A Fusion Cannon is a T'au version of a Melta Weapon, and fires blasts of directed energy produced by a nuclear fusion reaction which can reduce even the most heavily armoured vehicles or fortifications to slag in the blink of an eye.
The Fusion Cannon is essentially a larger version of a Battlesuit-mounted Fusion Blaster. The Fusion Cannon has an extended range compared to a Fusion Blaster, and a larger blast radius that allows its fire to destroy closely packed groups of enemy vehicles and heavy infantry.
The Fusion Cannon was first encountered by the armed forces of the Imperium of Man during the Taros Campaign, where Imperial tacticians believe the weapons were being field-tested for the first time by the T'au Fire Caste.
- Imperial Armour Three – The Taros Campaign, pp. 158, 162