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.
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 siege to Helmgart.
Around this time, Bogdan and Golgfag sack Bugman's Brewery.
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.
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.
Originally hosted over at:
The College of Speculative Antiquarians: The War of Grom the Paunch - alternative timeline:
In this timeline, it is the killing of Bono, son of Joseph, Bugman by Bogdan Legbreak and Golgfag the Rutdrogg that leads to Joseph Bugman to form his famous Rangers. The Rangers are exterminated, and Joseph disappears never to be seen again, presumed killed, when Bogdan and Golgfagg sack Bugman's Brewery. Indeed, Goblin legend tells of how Bogdan taunts and kills Joseph Bugman during the sacking of the brewery.
The stories of Bugman's return from the sacking of the Brewery and the refounding of the Rangers at Karak Varn seem not to based on early historical record. In even later stories, Bugman does not even found his Rangers until after the sack of the brewery. Finally, in the latest versions of the story, generations are transposed. In the earliest versions, Joseph is the grandson of Samuel Bugman, and Bono Bugman is Joseph's son. Later, Samuel is sometimes called Bugman's father; meanwhile, Bono is sometimes called a son of Samuel.
The sacking of Nuln, sometimes said in later tales to be the work of Grom the Paunch (of the Misty Mountain, as he is always known in the earliest tales), is here credited to Mudat Brokenbone. Though, after the sack of Nuln, later stories say that Grom was defeated by the Prince of Altdorf and attacked Middenheim, this is treated as an Imperial rather than a Dwarf city; and Grom is said to have personally broken the gates of the city and built a chariot there from the remains of a temple to Ulric. Thus, the use of chariots by the Goblin army is credited to Grom, whereas in the early tales it is Bogdan and Hogg who command them. He is than given a story of invading Uluthuan, whereas in the earliest version, he was killed in the siege of Middenheim.
In the earliest versions then, three Greenskin leaders (Grom the Paunch of the Misty Mountain, Mudat Brokenbone and Bogdan Legbreak) command the forces that attack the dwarf cities and invade the Empire. Later tales only remember Grom the Paunch and ascribe all the deeds to him that in the earliest tales are the work of other commanders.