With no functioning command staff, due to them being very much dead, a Colonel-Commissar by the name of Ibram Gaunt was assigned to look after the regiment.
Only one full regiment was able to make it off planet. To bring a long story short, Tanith was destroyed by the forces of Chaos just shortly after they finished mustering three regiments (We did it before it was cool to do so, Cadia). 3 Notable Ghosts (Spoilers through His Last Command).The Tanith First and Only are largely the subject of Dan Abnett's acclaimed Gaunts Ghosts series, starting with the aptly named(When it was originally published)"First And Only". It is currently engaged in the Sabbat Worlds Crusade under Warmaster Macaroth. The regiment was made famous by Colonel-Commissar Ibram Gaunt. Even the dark, mysterious forests of their lost homeworld is a nod to the ancient Roman descriptions of Scotland and Ireland.
The Tanith people are predominantly Celtic, a mixture of Welsh, Scottish, and Irish as evidenced by their common appearances(Black Irish - pale skin, blue eyes and dark hair), in addition to their frequent use of bagpipes on the battlefield to boost morale, their names (The Scottish Mk- prefix and Welsh l's, y's and w's), woad tattoos and Sgian-dubh-style silver knives. Both of these skills have proven invaluable over the history of the regiment. This granted Tanith's population an inborn sense of direction, as well as an uncanny ability to camouflage themselves. Tanith was home to the famous Nalwood trees, rumored to roam her forests, causing hapless travelers to become helplessly lost.
The Tanith First (And Only) are an Imperial Guard regiment founded on the forest planet Tanith. "Happy are those whose walls already rise!" – Aeneid, Virgil Home is home, however poor it may be." – Welsh Proverb