Moats and walls are pretty good analogies here. The magnitude of the barrier provided by a moat was considerable in the 1300's. By the late 20th century, it was

Moats and walls are pretty good analogies here. The magnitude of the barrier provided by a moat was considerable in the 1300's. By the late 20th century, it was far less. https://www.youtube.com/watch?v=bWMrY49qqDw https://www.youtube.com/watch?v=bWMrY49qqDw In the 11th century, a wooden palisade or an earthen berm fortification could be held for something like a half year. By the end of WWII, it constituted a delaying tactic. https://en.wikipedia.org/wiki/Rhino_tank https://en.wikipedia.org/wiki/Rhino_tank A phase change happened with military tactics in the lead-up to the 1st half of the 20th century, where the power of mobile mechanized armor and air support greatly reduced the value of fortifications. That said, I don't think moats are dead. It's just that the time-scales have changed.