I use to find it strange that Castiel served in Ishim’s garrison. I mean, angels don’t die or retire. From what Anael told us in season 13, promotions aren’t a regular thing in Heaven, and the show never drops any hints about enemies who could have been killing off angels aside from demons, who, judging by all the trouble Azazel went to in pulling off his masterplan without violating any “rules” as he put it, must have been pretty well under control before the Hellgate was opened. How did Cas get his own garrison by the time we met him?
And then I realized, angels don’t naturally die or retire, but they are capable of something else.
The garrison Castiel took over probably belonged to Anna, who we know fell after 1901, because she was raised from a child by her parents on earth, and season 5 confirmed that she was in a position to issue orders to Uriel, which fits with Uriel being Castiel’s subordinate when he’s introduced in season 4. Considering that Naomi tells us that Castiel had been rebellious and unreliable since the time of Moses and the plagues, Ishim probably used his status in Heaven to get his pet the job, which could have contributed to the resentment we see when he and Cas meet again in season 12. Go back and watch the flashbacks from 1901, it’s clear that Castiel is Ishim’s second in command. And it must have taken a lot of time and effort to coax Castiel from problem child to right hand man. There had to have been a bond there.
And if Cas had been a brand new baby captain, Ishim might have been pulling strings to set him up with chances to prove himself---he might have even tried to fight the decision to demote Castiel in favor of Uriel in the middle of season 4. Saving Dean from Hell could very well have been the first major assignment Castiel undertook in a leadership role.
And you know, it must have been really bitter for Ishim to watch Cas throw all of his good will away for what must have looked like the same toxic human infatuation that Ishim looked down on while secretly indulging in himself.
I’m not saying that this is indisputably what happened, but I do love when the details a show throws out over the course of seasons fit together. And even if I’m wrong, Castiel still only could have been a captain for a little over a century at most. To an immortal being, that still must have seemed like nothing.