There was a time, long ago, when any man might kill another in Europe and not be punished for his deed. It was not thought wrong to take human life. Today it is not considered wrong to kill, provided a man is ordered to do so by his general or his king. When two kings go to war, each claiming his quarrel to be a just one, wholesale murder is done, and each side is made by its government to think itself very virtuous and wholly justified in its killing. It should be the great aim of everyone today to help to bring about lasting peace among all the nations. [Illustration: A Drill Ground in Modern Europe.] In order to know how to do this, we must study the causes of the wars of the past. We shall find, as we do so, that almost all wars can be traced to one of four causes: (1) the instinct among barbarous tribes to fight with and plunder their neighbors; (2) the ambition of kings to enlarge their kingdoms; (3) the desire of the traders of one nation to increase their commerce at the expense of some other nation; (4) a people’s wish to be free from the control of some other country and to become a nation by itself. Of the four reasons, only the last furnishes a just cause for war, and this cause has been brought about only when kings have sent their armies out, and forced into their kingdoms other peoples who wished to govern themselves. Questions for Review Why must foreigners in the United States return to their native lands when summoned by their governments? How is it that war helps to breed diseases? Is race hatred a cause of war or a result of it? Whom do we mean by the government in the United States? Who controls the government in Russia? Who in England? Who in Germany? Who in France? In Southey’s poem, how does the children’s idea of the battle differ from that of their grandfather? Why? Are people less likely to protest against war if their forefathers have fought many wars? What have been the four main causes of war? Chapter II. Rome and the Barbarian Tribes New governments in Europe.—Earliest times.—How civilization began.—The rise of Rome.—Roman civilization.—Roman cruelty.—The German tribes.—The Slavic tribes.—The Celtic tribes.—The Huns and Moors.—The great Germanic invasions of the Roman world.