Calling in the Hellhounds - Putin to Isis: Hey, They'll Respond - Look at Syria (from 2015 on)...& Don't Forget What Putin's Government Did to Grozny, Chechnya (from 1999)...& to Georgia (in 2008)

Birds of a feather (ever) flock together (or some such metaphor)...

No, that's grossly insulting to your average bird...

Infinitely more apt would doubtless be the biblical reference to the very last days of Earth's history, at/after which point of time there are corpses galore...

And the gospel writer simply adds:

...wheresoever the carcase is, there will the eagles be gathered together...

Or maybe even the vultures, for that matter...