From the earliest annals, which may or may not be the most correct, the following rough timeline can be constructed.
Grom kills Wulfrun Willowhand, King of the Northern Dwarfs, beginning the Dwarf-Goblin Wars.
At some point subsequently, Mudat Brokenbone sacks Nuln; around this time, Bogdan Legbreak, a Goblin warlord with many chariots, and his Ogre ally Golgfag the Rutdrogg, kill Bono Bugman.
Following the sack of Nuln, Mudat lays seige to Helmgart.
Around this time, Bogdan and Golgfag sack Bugman's Brewery.
After the Seige of Helmgart, Mudat and Grom end up on opposite sides in the Battle of Gonnear; Grom kills Mudat. This is the first recorded appearance of Grom's Goblin Guard.
Some time after this, Golgfag's second-in-command Gratthud slays Bogdan; 'Mad-Eyed' Hogg becomes the leader of Bogdan's chariots, and commands them at Zhuf Field, where he fights alongside Grom.
After Zhuf Field, Grom and Hogg assault the 'Dwarf City' of Middenheim, where Grom is killed.
Some years later is the battle of Mad Dog Pass, where Grom's Goblin Guard is exterminated. Hogg is also present at the battle, and leads the survivors of of Bogdan's chariots into the Darklands.