There is no question that the Islamic State will be defeated in Mosul; the real question is what comes afterward. Can the post-Islamic State effort resolve the squabbling likely to arise over numerous issues and bring lasting stability to one of Iraq's most diverse and challenging provinces? Failure to do so could lead to ISIS 3.0.

Iraq's Sunnis need to be brought back into the fold. They need to feel as though they have a stake in the success of Iraq rather than a stake in its failure.

Leadership is an individual sport, one that has to be fine-tuned to each of the people that reports to you. Leaders also need to provide the direction, energy, encouragement and inspiration for each person who reports directly to the leader as well as for the overall organization.

When I was commander of Central Command, obviously we were very concerned about the developments in Yemen, the developments in Somalia and elsewhere, in Africa and so forth. But the al Qaeda senior leadership is under unprecedented pressure.

In all of our efforts, we continue to emphasize the importance of inclusivity and transparency on the part of the Afghan government and leadership, especially in linking nascent local governing institutions to the decision-making and financial resources in Kabul.

You have to keep on disrupting. If you let up the pressure, then al-Qaeda senior leadership will come back.

Even before the missteps that I've had, I was never going to run for office. My family is adamantly opposed to it, and frankly, my politics don't necessarily work for the primaries of either of our parties.

All Americans should take great pride in the men and women serving our nation in Iraq and in the courage, determination, resilience and initiative they demonstrate each and every day. It remains the greatest of honors to soldier with them.

I considered our British comrades to rank with the finest men and women of any armed service in the world. And I know that my fellow American soldiers - and those of the other coalition countries under my command - valued very highly the professional expertise, capability, courage, and determination of our British partners on the battlefield.

There is nothing I can do to undo what I did. I can only say again how sorry I am to those I let down and then strive to go forward with a greater sense of humility and purpose, and with gratitude to those who stood with me during a very difficult chapter in my life.