[Stavka2]

Oh, darn it, you found me out...gasp.

Well, since you are soooo smart, you must have missed these while you were at it...

The Tsar at Stavka

or

A historic synopsis of Stavka and the Russian Army in WW1

Do try a little harder next time.

[BlueLancer]

True, but the only thing that I could find was that Stavka appears to be used as a place name as in "The Tsar at Stavka" or "The Tsar moved to Stavka". There is nothing to show in Google or DogPile that "Stavka" was used as a meaning for the Russian High Command prior to WWI. So, except for that short period before the Revolution, it would appear that the term wasn't used to designate the High Command before that, akin to using "The Pentagon" (a place name) to reference the US military High Command.