如果你的论文题目是”日本对中国的侵略”，而你论文的开头又是这样写”在本文中，我将讨论1938至1945年日本入侵中国。” 你的文章将没有真正的开头。

If your paper is entitled "The Japanese invasion to China" you will have made no real beginning if you start out by writing:"In this paper, I will discuss the Japanese invasion to China of 1938-1945.

youdao

It's never--it probably wasn't quite that easy but the invading side goes for something that the other side will have to defend and that determines when the fighting takes place.

可能不会这么简单,但当入侵方为了某一目进行侵略,被侵方就不得不防守,这就决定了战争的爆发时间

耶鲁公开课 - 古希腊历史简介课程节选

So imagine the following example, an invader is thinking about invading a country, and there are two ways -- there are two passes if you like -- through which he can lead his army.

想象一下这样的例子,一个侵略者打算入侵一个国家,有两条路,想象成两个关口也行,侵略者必须通过一个才能进入

耶鲁公开课 - 博弈论课程节选