It is important to signal that opposition to the use of any weapon of mass destruction is both deep and broad.

The United States, working closely with the United Kingdom and others, established the liberal world order in the wake of World War II. The goal was to ensure that the conditions that had led to two world wars in 30 years would never again arise.

The vote in the United Kingdom in favor of leaving the E.U. attested to the loss of elite influence.

The rise of populism is in part a response to stagnating incomes and job loss, owing mostly to new technologies but widely attributed to imports and immigrants.

Russia may well be willing to stop interfering in Eastern Ukraine in exchange for a degree of sanctions relief if it could be assured that ethnic Russians there would not face reprisals.

It is true that the U.S. could and should have been more generous as Russia made its painful transition to a market economy in the 1990s.

Indeed, the big U.S. error after 9/11 was to treat Pakistan as if it were an ally. With an ally, it is possible to assume a large degree of policy overlap. With Pakistan, no such assumption can be made.

Bad situations can always get worse.

American presidents get to make lots of choices, with one critical exception: what awaits them in the in-box on top of the desk in the Oval Office.

The United States is not just another country. It has more capacity and potential to influence the world than any other country - and no other country has the resources and mindset to lead a world that is not on autopilot.

Paradigm shifts, particularly in diplomacy and security issues, are, by definition, major undertakings.

Americans never would alter the way entitlement programs are funded or education administered without serious study and widespread debate.

Security is the absolute precondition for sustainable recovery from conflict; without it, people cannot rebuild their country or return to school or work.

History shows that societies where opportunity is safeguarded tend to be societies that are good international citizens.

No country can succeed if it denies itself the talents of half of its people.

Americans, for their part, must accept that a strong Europe will not be content to simply do America's bidding.

It is neither feasible nor desirable for Europe to establish itself as a geopolitical equal or competitor of the U.S.

In a global world, what happens within one country can all too easily affect others.

Russian membership in the World Trade Organization has the potential to strengthen the rule of law, combat corruption, and give Russia a stake in better relations with the outside world.

The benefits of freer trade, such as job creation, lower inflation, and greater consumer choice, are often invisible or only partly visible.

Weapons of mass destruction - nuclear, biological, and chemical weapons - are just that, and no cause can excuse their use.

The United States emerged from the Cold War with unprecedented absolute and relative power. It was truly first among unequals.

The decision to attack Iraq in March 2003 was discretionary; it was a war of choice.

There is no getting around the reality that the second Iraq war was a war of choice; had it been carried out differently, it still would have been an expensive choice and almost certainly a bad one.

Dissent is as American as cherry pie.

I did not support the U.S. decision to intervene with military force in Libya. The evidence was not persuasive that a large-scale massacre or genocide was either likely or imminent. Policies other than military intervention were never given a full chance.

Foreign policy must be about priorities. The United States cannot do everything everywhere.

America must reduce its fiscal deficit, modernize its infrastructure, and improve its schools.

On occasion, terrorists will succeed despite our best efforts. That is part of the legacy of 9/11. But 9/11 also shows us that while terrorists can destroy, they are unable to create.

If you assume away most or all of the questions or difficulties, you can persuade yourself of just about anything.

If anything, what happened in Iraq after the fall of Saddam set back prospects for democratic reform in the region, as many came to associate political change with chaos.

White House staff are meant to coordinate and set policy, not carry it out.

The first Iraq War was one of necessity because vital U.S. interests were at stake, and we reached the point where no other national-security instruments were likely to achieve the necessary goal, which was the reversal of Saddam Hussein's invasion and occupation of Kuwait.

There's a pattern in Bush 43's presidency of being attracted to the big and the bold, and my whole reading of him is that he was instinctively uncomfortable with what you might call a modulated foreign policy - a foreign policy of adjustment, of degree.

When great powers fade, as they inevitably must, it's normally for one of two reasons. Some powers exhaust themselves through overreach abroad, underinvestment at home, or a mixture of the two. This was the case for the Soviet Union. Other powers lose their privileged position with the emergence of new, stronger powers.

Donald Trump's United States is not isolationist. He has authorized the use of limited military force against the Syrian government in a manner his predecessor rejected.

Trump is the first post-World War II American president to view the burdens of world leadership as outweighing the benefits.

Trade accords had been a staple of the post-World War II world, providing a mechanism for economic growth, development, and association with friends and allies, and a means of reining in would-be adversaries who otherwise would have little incentive to act with restraint.

What is obvious is that Donald Trump is comfortable with an approach to running his presidency based on what worked for him in the private sector.

Any time you use military force, you have got to have a clear purpose that military forces can achieve.

I tend to be one of those who does not equate democratization with the holding of elections. The emphasis ought to be on such things as rule of law, economic reform, and promotion of a free media - in short, essentially independent, free institutions.

Vietnam was not a war of choice the United States had to fight. It was clearly not central.

For President Bush, the first, the 41st president, George Herbert Walker Bush, I spent all 4 years of his presidency on the staff for the National Security Council.

There is no way to know for certain what accounts for North Korean decisionmaking, given how closed a country it is.

No amount of sanctioning will persuade North Korea to give up nuclear weapons, nor will China step up and solve the problem for us.

How can we pressure China on North Korea if China's one of the two largest holders of American debt?

Our inability to govern ourselves at home, to deal with everything from infrastructure to our debt to tax policy, is reducing the appeal of the American model.

I did not believe in the Iraq war.

Campaigning and governing are two very different activities, and there is no reason to assume that how Trump conducted the former will dictate how he approaches the latter.