Name : The Corinthian Crusade
Source: WD264 (page 47)
When : 690/1?.M41 - 698.M41
Where: Corinthe, Dominion of Storms, Segmentum Ultima
Who : Unkown Black Templar numbers allived with Ultramaines, Lamenters, Marines Errant, Angels of Absolution, Silver Skulls and over fifty Imperial guard regiments versus the Xenos Orks led by Skargor the Despoiler.
What: Over fifty Imperial Guard regiments and detachments of six Adeptus Astartes took part in this Crusade. It was intended to liberate the star system of Corinth from the Ork Warlord, Skargor the Despoiler. Skargor's Waaah was slowly pushed back to the world of Corinth itself, where he had been building and improving on the planet's already formiddable defences. The planning of the operation was given to the Space Marines of the Ultramarines Chapter.
Within three months the Imperial Forces had secured a landing and had pushed Skargor back into a siege of the planet's principal fortress. soon the artillary of the Imperial Guard had created a significant breach in the outer defences and the Ultramrines Chapter Ancient Galatan stormed the breach carrying the Banner of Maccrage.
Thousands dies in the nine day effort to storm the breach. Skargor lead the defence personally, but the attackers inexorably forced the orks back, until on the 9th day Warboss Skargor met Ancient Galatan in single combat. Skargor was finally thrown down and the breach taken, but it cost Galatan his life.
Why: To relieve the Corinthe system
Notes: There isnt any mention of the Black Templar in this extract, are there other sources indicating the Chapters involvement that anyone knows of?
EDIT: I will need to track down the article in full, however found some more tidbits from other forums:
In reference to Sword Brethren Rammius:
and at Corinth, he toppled an Ork Dreadnought to save the life of Marneus Calgar, Chapter Master of the Ultramarines