正文：

Civil wars are fought between citizens of the same country and are fought within the country.

内战是在同一国家的公民之间进行的，并且是在国内进行的。

If citizens of a country disagree about a policy or leader, they may fight a civil war.

如果一个国家的公民对政策或领导人不满意，他们可能会打一场内战。

A world war is fought when countries form alliances, and these alliances fight each other.

当国家结成联盟时，就会发生世界大战，而这些联盟又相互争斗。

A world war involves many or most of the world's most powerful countries.

世界大战涉及许多或大多数世界上最强大的国家。

There were 2 world wars in the 20th century.

20世纪有两次世界大战。

Terrorism involves groups of individuals rather than countries.

恐怖主义涉及个人团体而不是国家。

Terrorists may come from different countries, and they may share the same beliefs.

恐怖分子可能来自不同的国家，他们可能拥有相同的信仰。

Terrorists often use car-bombings and suicide attacks on innocent people.

恐怖分子经常对无辜的人使用汽车爆炸和自杀式袭击。

A terrorist attack can happen at any time and any place.

恐怖袭击可能随时随地发生。

An invasion occurs when one country attacks another.

当一个国家攻击另一个国家时，就会发生入侵。

It sends its army into the other country, and attempts to take control.

它派军队进入另一个国家，并试图控制。

One of the most famous invasions was when France invaded Russia in 1812.

最著名的入侵之一是 1812 年法国入侵俄罗斯。

A defensive war occurs when a country is attacked and needs to defend itself.

当一个国家受到攻击并需要自卫时，就会发生防御性战争。

Most countries have a military so that it can defend itself if it's attacked.

大多数国家都有军队，因此如果受到攻击，它可以自卫。

When France invaded Russia in 1812, the Russian army fought a defensive war and defeated the French army.

1812年法国入侵俄国时，俄国军队打了一场防御战，打败了法国军队。

题目：

Civil wars are often fought when one part of a country wants to become an independent country.

当一个国家的一部分想要成为一个独立的国家时，经常会发生内战。

Throughout history there have been many invasions.

历史上有过多次入侵。

Sometimes two leaders will fight for power within a country and start a civil war.

有时，两个领导人会在一个国家内争夺权力并引发内战。