The Rhine Bridge (https://en.wikipedia.org/wiki/Caesar%27s_Rhine_bridges) is a good example.

Caesar comes, builds a bridge over a significant river, because why not, peeks on the other side and tears it down again. No big deal, he can build another any time.

Interesting to also look at how US troops finally got the upper hand in urban Iraq, with large amounts of concrete walls of varying sizes. In the film "American Sniper" you can see the walls getting put up under fire from an expert Iraqi sniper. Not sure about the accuracy of the film, but I believe the walls were pivotal in the success.