The more people will be materialistic, the world will be burdened. Therefore there must be war, pestilence, famine, to clear these rascals, clear out. You'll find these things. In Europe, every ten years, twenty years, there is a fight, war. It is the history. From the Greece history, Roman history and Seven Years War, Hundred Years War — wars. There must be war, because they are sinful. The same sinful, killing animals continually. So there is war, reaction. So what is that war? To lessen the burden. To lessen the burden. It becomes very heavy, unbearable by the earth. And to reduce the weight there is natural… And when there is still more power required, then Krsna comes: "Arrange for a war in the battlefield of Kuruksetra and bring all the rascals and finish within eighteen days." Within eighteen days, sixty-four crores men died.

(From Srila Prabhupada's lecture on Srimad-Bhagavatam 1.7.25 — September 22, 1976, Vrndavana)