I just successfully walled an opponent off from their allies in a 3v3 Black Forest game.

It was pretty satisfying. I was in the pocket position but the map was explored and there was a pathway near the middle. I snuck two villagers and my scout, survived four wolf attacks, then found a little cave in the forest to hide and chop wood with a lumber camp. Once I got to Feudal Age I built an archery range in that little cave and queued up archers. Then I took them out, stonewalled my target's only connection to their allies, and started raiding his base. By the time their ally sent units to help there were two layers of stone wall blocking them, and when the target tried to retreat their villagers to their ally's base they were also trapped in.