Pressure bombs were weapons used by both the Galactic Republic and the Honorable Union of Desevro & Tion in the Tionese War. They were designed to release a vast quantity of sheer pressure when detonated, causing widespread damage.
During the Tionese War, the weapons were first deployed by the Union navy during attacks on outlying Republic shipyards. Both sides sent fleets up and down the Perlemian Trade Route and bombed their respective capitals of Coruscant and Desevro throughout the century-long conflict.
When the Republic mounted its last counter-offensive with a newly-launched star fleet, turning the tide of the conflict, they made an example of Desevro itself, refusing the Union's offer of unconditional surrender and laying waste to the planet with a sustained pressure bombardment from orbit that left the planet in ruins.
Hethrir would later use pressure bombs during the Empire Reborn crisis.