(Semi-cd) Smart widow mine placement and a bit of micro definitely helped the Marines take the forward bases in the Kursk sector.
We've yet to see how much attack-move it will take for the Zerglings to reach the Pokrovsk base. (/semi-cd)
But as I have stated before as Executor, really the best thing is to just go for the base trade. Trade Moskvá for Kiev, swap your entire territory for the other and everyone's equally satisfied. We've arbitrated several conflicts in the local galaxy this way before, and so far no one has gotten upset enough to usurp the mighty Golden Armada. I'd consider this successful negotiation.