Well if you're not defending the easy pass, he doesn't lose anyone, and if he attacks through the hard pass he's going to lose at least one battalion.

如果你没有在平坦之途设防他兵力不减,然而如果他从崎岖之途进军,那么他将至少损失一个营

耶鲁公开课 - 博弈论课程节选

These were not defended. Your farmland was not defended.

没有防御工事,你的农场都是不设防的

耶鲁公开课 - 古希腊历史简介课程节选