Dean Fidelman said that he believes a climber's ego can be his worst enemy on a rock.

VOA: special.2009.12.09

Isn't the distinction between friend and enemy ? based on a kind of knowledge, on a perception of ? who is your friend and who is your enemy?

朋友与敌人之间的差别,不是根据知识吗，或是你对,谁是朋友或敌人的看法？

耶鲁公开课 - 政治哲学导论课程节选

Then it lands on your foot, because assuming the cannon is at zero height, the cannonball certainly comes out towards the enemy, but has no time of flight.

然后它就会落在你的脚边,因为假设大炮的高度为 0,炮弹笔直地出膛打向敌人,却没有时间飞行

耶鲁公开课 - 基础物理课程节选

He led troops on very dangerous attacks against the enemy.

VOA: special.2009.05.24

He says so-called enemy combatants, foreign fighters captured on overseas battlefields, should not be granted the protections of the U.S.

VOA: standard.2009.11.25

"As the engagement went on and the enemy continued with strong fire, air support was called for."

VOA: standard.2009.09.12

"We must keep in mind how even apparently unsuccessful attacks on Western mass transportation systems can bring major cities to a halt, cost the enemy billions and send his corporations into bankruptcy."

VOA: standard.2010.04.01

"We have faced an enemy who do not want to fight us force-on-force, rather they wanted to lay improvised explosive devices to halt us in our path and this summer total of 1,800 Improvised explosive devices laid in our path, so we have had to adapt quickly."

VOA: standard.2009.10.12