The strategic problem was this: the U.S.

Army could not use the Bozeman Trail.

It could build forts along the trail.

It could garrison those forts.

It could defend those forts against direct assault.

But it could not project effective military power beyond the walls of those forts, could not protect the civilian traffic the trail was supposed to serve, and could not suppress the sustained resistance campaign that made the entire enterprise unworkable.

This is not to say that the Lakota and their allies won every engagement.