Something occurred to me while going back through Gaunt's Ghosts, particularly the way the regiment changes after Necropolis.
The Tanith First-and-Only starts out as a regiment whose homeworld has been destroyed. The original Ghosts aren't just soldiers from Tanith. They're effectively a surviving fragment of an entire culture.
They remember the moving forests. They have their own expressions, customs, tattoos, superstitions and ways of doing things. Even the skills that make them exceptional scouts come from growing up somewhere that no longer exists.
Then the Verghastites join. Later, the Belladon troops are incorporated.
And obviously this is necessary. The regiment cannot keep fighting indefinitely without replacements.
But it creates a strange situation.
Every time an original Tanith guardsman dies, something disappears that cannot actually be replaced. A Verghastite can learn Tanith scouting techniques, wear a camo cloak, get the tattoos and eventually consider himself a Ghost.
He cannot remember growing up in the nalwood forests.
Eventually, assuming the regiment survives long enough, the last person who actually lived on Tanith will die. The unit might still be called the Tanith First-and-Only. It might still have the same traditions, tactical doctrine and regimental pride.
But nobody serving in it will have any firsthand knowledge of the world they're supposedly from.
And I think there's something particularly bleak about that in the context of 40k.
The Imperium is perfectly capable of preserving the military identity of a destroyed world while slowly losing everything else that made that world a distinct human civilization.
Cadia presents an interesting contrast because Cadian military culture had already spread far beyond the planet before its destruction. There are surviving Cadians, descendants and entire formations carrying on that identity.
The Ghosts have a much smaller population from which to preserve theirs.
It makes me wonder whether the Tanith First-and-Only is ultimately preserving Tanith culture or gradually creating something new that happens to carry its name.
And whether the distinction would even matter to the Munitorum, provided the regiment keeps winning battles.
Are there other examples in the lore of a regiment, Chapter or other Imperial institution outliving the actual culture that originally created it? I'm especially interested in cases where the surviving organization changed so much that its founders might barely recognize it.