User blog comment:Godisme/Everything But The Rain Op. 3 Dark of the Moon/@comment-1861226-20130316040117/@comment-5745799-20130322131757

I think the Squad 10 tragedy happened to the captain before Isshin. 110 years ago, Shinji was the captain of Squad 5. He was succeeded by his then-lieutenant, Aizen. At the end of the previous chapter, however, it shows that Gin, Aizen, and Kaname were all captains at the time, so the events of the chapter had to have happened fairly recently.