@leeways
Image mana as light, and magic as ways of using that light. except that normal humans cant see it, only mages.
now image everyone giving off an unique light, that is easy to ID as long as you have an accurate version saved.
Tanya being the one-person army that she is, an Ace of Aces, commander of a very powerfull wing and some other things, her appearing on the battlefield is bad news for anyone not on her side.
if they can detect her accurately, figure out where she's coming from and combine this with other intel. they might be able to set up a decent defense, and even kill her (or so they hope.)
kinda like radar nowadays and each ship giving off a ping, except each ping is very distinctive and tanya is a Capital Cruiser or smth along these lines.