There are two great tragedies in life: one is to fail to achieve one's grandest ambitions, and the other one is to succeed.

Putin needs to understand and feel in his gut that if the Chechens get a nuclear bomb, they're going to Moscow first, they're not coming to New York.

When a rapidly rising power rivals an established ruling power, trouble ensues. In 11 of 15 cases in which this has occurred in the past 500 years, the result was war. The great Greek historian Thucydides identified these structural stresses as the primary cause of the war between Athens and Sparta in ancient Greece. In his oft-quoted insight, "It was the rise of Athens and the fear that this inspired in Sparta that made war inevitable."

For interests that are vital to the U.S. - that is, essential for our survival and wellbeing - the U.S. should be prepared to use military force - including unilaterally, if necessary.

If the Britain and France had done what they were obliged to do under the treaty and sent troops to enforce the treaty when Hitler remilitarized the Rhineland, the German general staff would have turned Hitler out. And one would not have had a cause for war, and you wouldn't have had World War II.

The fact that there are now many entities that may have some loose affiliation with a former core Al Qaeda - or who have decided to fashion themselves as an affiliate or follower in the Al Qaeda jihadist tradition - as well as groups that are just inspired by the concept that they could also be the perpetrators of mass killing, means that there is a spectrum of threats.

When we succeeded in winning the Cold War, escaping a nuclear Armageddon that could have killed us all, the U.S. inevitably had a serious problem about an encore: what now for our place in the world?