Terrorism is really the only existential threat to America as we know it - as a free country that plays a leading role in the world.

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.

I think the election of Trump was an expression of what happens in ruling powers as they become alarmed.

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?

One of the three big factors that count against war in the relationship between China and the U.S. are, first, nuclear weapons and even a condition of mutual assured destruction. Secondly, one's got two economies that have become so deeply interlaced that a war between the U.S. and China would leave Wal-Marts empty and Chinese factories producing for nothing. Thirdly, climate - if between the two of us, we keep doing what we're doing, we can create a climate in which our grandchildren won't be able to live.

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

And I hope that we can learn the lessons of the past in looking at the current challenge that China poses to a ruling America.