He warned that an all-out assault on their neighbours would be folly.他警告说对他们邻国发起全面进攻实属愚蠢之举。Napoleon's army was sacrificed on the altar of folly in the disastrous Russian campaign.在灾难性的俄国战役中，拿破仑的军队成了这一愚蠢之举的牺牲品。Their pranks were just youthful folly. 他们的恶作剧不过是年轻人的愚蠢之举而已。