In military strategy, a choke point is a geographical feature (such as a valley or defile) which forces an army to go into a narrower formation (greatly decreasing combat power) in order to pass through it. A choke point would allow a numerically inferior army to successfully fend off a larger army since the attacker would not be able to bring his superior numbers to bear.

Like the one in Afghanistan in the early invasion.
We got hammered there. But no one knew about
it, till PBS did a piece on it years later.