Jericho VII was a major battle in the Human-Covenant War. It is referenced a couple times throughout the lore but it was first shown at the start of the novel of The Fall of Reach where 3 Spartan II teams (Including the Master Chief and Blue Team) were deployed as well as thousands of Marines and ODST's to fight the Covenant. The battle lasted nearly a week with a huge stalemate in orbit between UNSC and Covenant forces battling for the planet. Unfortunately Covenant orbital reinforcements arrived in system and forced the UNSC to either retreat or face total annihilation. The planet was glassed as the UNSC retreated from another defeat and colony lost. It's one of my all time favorite events from the Human-Covenant War and I've always hoped it were shown more in depth or even had it's own game or game segment.