[jwhitlark]

Fortresses, particularly those without an active defense, have a bad track record. Shields don't work without the ability to hit back. Or, as the saying goes, "It takes two sides to have a battle, but only one to have a massacre."

[jack-r-abbit]

Well, slowing a person down with a little harder to get through first barrier gives more time between first notice and first action. Some times just buying enough time to hide/flee can save lives.