When I was a young man, two books impressed me. They still do. One is Konrad Lorenz's On Aggression. An M.D. and a Ph.D. and a 1973 Nobel laureate in medicine and physiology, Lorenz established the field of ethology, the study of the behavior of animals within their natural environment.

In his prologue to his book, Lorenz wrote, "the subject of this book is aggression, that is to say the fighting instinct in beast and man which is directed against members of the same species." According to him, animals, particularly males, are biologically programmed to fight over resources and turf and this behavior is part of natural selection. To a great degree, aggressive behavior is innate.

The other book that influenced me is Robert Ardrey's The Territorial Imperative. He popularized and expanded on Lorenz's ideas. After reading Ardrey, a Book-of-the Month News reviewer asked: "Are we a territorial species? Do we defend ourselves, whether by war or other means, because we have learned to do so -- or because, as animals, we must?"

Lorenz and Ardrey provide the reasons for my embracing the Roman proverb Si vis pacem, para bellum, "He who wishes peace should prepare for war." (The full text goes on to say, "He who desires victory should carefully train his soldiers; he who wants favorable results should fight relying on skill, not chance.")

Today war is no longer confined to soldiers battling each other in uniforms. It now includes terrorists who do not wear uniforms, do not represent a sovereign state, and use civilian airplanes and motor vehicles to crash into buildings in order to kill their enemies.

Despite these changes, pacifists cling to the notion that war is always immoral and is never justified. They forget that soldiers, not sermons, stopped Islam from advancing into Christian Europe at the Battle of Vienna in 1683. It was not sermons, but soldiers, who freed the American colonists from Great Britain's rule in 1781. It was soldiers, not sermons, who emancipated America's slaves in 1865 and who liberated the survivors of the Nazi death camps in 1945.

Counterterrorism is the predominant form of contemporary war.

After the attack on New York's World Trade Center, on 11 September 2001, Americans divided themselves into the September 10th people, the September 12th people, and the September 13th people. The September 13th people blame the United States for September 11th and think that the proper U.S. response is to abandon American "arrogance" and American support of Israel. The September 10th people reject these notions, but think that terrorist acts are crimes that should be countered only by our law-enforcement and intelligence communities. The September 12th people believe that Islamic terrorists want to destroy Western civilization and that their acts of terrorism are acts of war that we must counter with mainly military responses.

When it comes to terrorism beyond our borders, passages from an article I published in 1979 come to mind:

  The essential question -- and it will cause us great pain in every sense if any of the American hostages now being held in Iran are harmed or are still being held when these words are printed -- is the extent to which the Western world in general, the Third World in particular, and the United States especially, are themselves responsible for this governmentally condoned terrorism.

  In its most recurring form, modern terrorism has manifested itself in the confrontation between the Arabs and the Israelis. . . Decades ago, Israel warned the world, particularly the Western nations, that internationally tolerated terrorism is a political virus that knows no boundaries. If left unchecked it would spread to other causes, continents, and countries.

  So long as they thought they were immune from the terrorist virus, aloof bystanders could adopt this kind of logic and base their actions and inactions on it. But there are no aloof bystanders. The Tehran terrorists have proven that once and for all. If the countries of the West do not band together against terrorism, whatever the short-term term economic sacrifices, their long-term future as truly sovereign states is problematical.

Those who hate America like to discuss war within the framework of American imperialism and colonialism. Yes, the United States took land from the native peoples of North America. But so did the French, British, and Canadians. So did the Spaniards and Portuguese in Latin America. So did the Australians and New Zealanders in the South Seas. So did the Russians, Chinese, and Japanese in Asia and Europe. Did the Scots, Welsh, and Catholics of Northern Island want to be a part of Great Britain? Do the Tibetans want to be part of Communist China?

 It is true that the United States conquered the Philippines and Puerto Rico in the 1898 Spanish-American War and remained in de facto control of Cuba until 1934. But America gave the Filipinos their independence in 1946, and it has promised statehood or independence to the Puerto Ricans whenever they want to have it.

It is true that President Theodore Roosevelt, influenced by U.S. Admiral Alfred Thayer Mahan's sea-power theories, took advantage of a revolt against Colombia to acquire what became the Panama Canal Zone in 1903. But President Jimmy Carter returned both the Zone and the Canal to the Panamanians in 1977.

It is true that in 1945, President Harry Truman ordered the dropping of atomic bombs on Japan thus ending its participation in World War II. It is true that for a few years, the United States was the only power with nuclear weapons but it blackmailed no one. Nor did it take anyone's land. By contrast, the Soviet Union incorporated huge swaths of post-war Poland and Germany.

If one compares the United States to Assyria, Babylonia, Persia, Greece, and Rome -- or to Ottoman Turkey, Spain, Portugal, Japan, Russia, Britain, and France -- one can only conclude that the United States was and is the least warlike and least imperialistic super power in history.

The just-concluded agreement between Iran and the United States, Russia, China, Britain, France, and Germany raises the question of nuclear war,  something which Israel fears existentially.

In 1981, when Iraq threatened Israel, Israel's then Prime Minister, Menachem Begin, ordered the Israeli Air Force to destroy Iraq's nuclear reactor and declared that "Israel has nothing to apologize for. In simple logic, we decided to act now, before it is too late. We shall defend our people with all the means at our disposal."

Now, one sometimes hears the argument that if Iran can live with an Israeli bomb, why can't Israel live with an Iranian one? The answer is that no Israeli leader has ever threatened to eradicate Iran. Iran is a large country. Israel is a tiny one. Israel's nuclear arsenal can deter its enemies only if they have the wisdom and sanity to be deterred.

During the Cold War, the Russians and the Americans operated under a political and military doctrine known as MAD, mutual assured destruction. It assumed that no matter how bad things got between the Soviet Union and the United States -- the 1962 Cuban missile crisis is a case in point -- neither side would risk annihilation.

The leaders of Iran do not think that way. They reason as follows: We have 70 million people, and Israel has 7 million. If we attack the Zionists with nuclear bombs, they will respond in kind. If they are lucky, they will kill half of us, but if Allah wills it, we shall kill all of them, and there will still be 35 million of us left.

In sum, we humans may enjoy periods of peace -- sometimes for a long time -- but we shall never rid ourselves of war because we are "wired" to fight over pieces of land, even useless pieces of land. I am afraid that Konrad Lorenz, Robert Ardrey, and Publius Flavius Vegetius Renatus (the man who coined the Latin phrase Si vis pacem para bellum) are correct. So, too, is Max Boot, the American author and military historian. Boot rejects the "sunny, if ahistorical, Enlightenment faith that peace is the natural order of things and war a temporary aberration."

This is the world in which we have lived in the past. This is the world in which we live now. And this is the world in which we shall live in the future.

Based on part on my article "An Old Man's Thoughts on War and Peace," in Military Review, May- June, 2011