The United States has to be a leader in the world, because the problem is: If we are not leading, nobody else will.

We are a nation at war. This is also a time for hard choices. It's about ensuring that we are able to prevail in the conflicts in which we are now engaged. But it's also about being able to be strong and disciplined in applying our nation's limited resources to defending America.

Go forward, knowing that you are greater than the challenges of your time.

One of the principal qualities that you need as national security adviser is trust, the trust of the president. And that depends on truth and it depends on honesty.

I think it's extremely important that the president Donald Trump himself indicate that he too wants to discover the full truth behind what the Russians did to elections 2016.

If the Iraqis fail to implement the reforms, if they fail to get a handle on the violence, there's nothing the United States can do, militarily or otherwise, that can solve those problems. They have to assume the primary responsibility to govern themselves.

Obama really does recognize the threats that are out there; I think he understands the world. He understands the role of America in that troubled world.