Humbarine was an ancient ecumenopolis and a Core Founder. It was the capital world of a rich and heavily industrialized sector. The planet was also loyal to the Republic during the Clone Wars, thus making it a target for the Separatists.
Some time following the conquest of Duro, a CIS fleet under General Grievous's flagship Invisible Hand launched several assaults on Humbarine. This included an hour-long orbital bombardment that melted the crust of the planet, thus destroying the planetwide metropolis and presumably killing much of the population.
Survivors from the sector defense forces, like Barrow Oicunn, were relocated to other Republic units for the remainder of the war. With additional planets in the sector falling to the CIS, the entire Humbarine sector was eventually considered lost to the Separatists and abandoned by the Republic.
This battle, along with CIS assaults on 26 strategic Loyalist worlds in the Core and the release of the Loedorvian Brain Plague into the Weemell sector (which wiped out almost every Human there), likely contributed to much of the Humanocentric policies of the Galactic Empire.
- Star Wars: Revenge of the Sith Incredible Cross-Sections (First mentioned)