Very few in-setting have any clues as to the source of uma reincarnation; namely Neo Universe (aware of alternate realities), Stay Gold (aware their past life to an extent), and possibly Manhattan Cafe (can see spirits). Beyond those 2 maybe 3, those aware of horses are practically non-existant.
Ah, i thought it was more understood.
Shiro father in chapter 1 talks about how Umas has some memories of past lives, so at least in this fic it's different (they don't necessarily need to understand that the memories come from their lives as horses and only from one past life as Uma).
While the emails being accidentally forwarded by her trainer makes sense, it would be a far funnier explanation if her networking with the security team resulted in them making absolutely certain she knew (as an undercover security guard).
Oh, there's a thought. Maybe Being X got so annoyed with Tanya that it incarnated her as a war animal or something and then the Three Goddesses cold clocked him.
No, warhorses are very much still in living memory. Horse cavalry was still used to great effect in WW2, mainly on the vast steppes of the Eastern Front and China, as a cavalry unit can move faster than a foot infantry unit the same size while taking up far less resources than an equivalent armored or motorized unit. Hell, as recently as Afghanistan there's been the occasional use—turns out it's far easier to get a horse up a mountain than a truck, so they're very useful for transportation, and there was even the occasional cavalry charge.
