Gen. David Petraeus weighs in on Iraq War, 20 years later

On the 20th anniversary of the allied invasion of Iraq that marked the start of the eight-year conflict, there are still some deep reflections and questions about the toll of the battles.

"Nightline" co-anchor Byron Pitts spoke with retired Gen. David Petraeus, who was in charge of commanding the multinational forces, about the war, 20 years later.

BYRON PITTS: General, thank you so much for joining us. We're grateful for your time. First question to you, sir. We just heard about some of the emotional trauma that these veterans of the Iraq War are still going through. Do you think the U.S. is well equipped to take care of them and are we doing enough?

GEN. DAVID PETRAEUS: I don't think we can ever do enough, frankly, for those who volunteered at a time of war, served and often did multiple tours in Iraq or in Afghanistan. They really should be regarded as America's new greatest generation.

And frankly, I feel a deep appreciation, [and] personal gratitude for the opportunity to have served with these great young men and women in uniform, again, all of them volunteers at a time of war.

PITTS: In 2007, you were appointed to command the multinational force in Iraq and put in place plans for a troop surge of 30,000 soldiers. That year would prove to be one of the deadliest on record. You were sharply criticized at the time for the troop surge. When you look back on it, do you wish you'd done things differently?

PETRAEUS: I actually thought we got it right during the troop surge.

We drove violence down by some 85 or 90% during the 18 months of the surge, and I commanded it a bit longer than that. We gave the Iraqis a wonderful new opportunity.

They did well. For the subsequent three and a half years until tragically, very soon after our final combat forces departed, the prime minister pursued ruinous sectarian actions…and allowed the Islamic State to reconstitute itself.

PITTS: Iraq, this is a country that lost hundreds of thousands of Iraqis, as close to 4,500 Americans were killed. We now live at a time, 20 years later, where there's a generation of Americans who have no real appreciation for what happened. But those families always will. So for them, was it worth it?

PETRAEUS: I leave that question to others, Byron, and for a very significant reason. And that is that I wrote more letters of condolence, I think, to America's mothers and fathers than any other commander having commanded there for some four years as a two, three and four-star [general], including during the surge in Iraq.

They actually share a degree of pride in what their soldiers did.

PITTS: [What is your] greatest regret? [What is] the thing you're most proud of?

PETRAEUS: Well, the greatest regret is that Iraq has still not fulfilled the hopes that certainly we had, but, more importantly, that the Iraqis had when we toppled the Saddam Hussein regime.

Iraq is still very much a work in progress. It is a country beset by political nepotism, corruption, terrible bureaucracy [and] inadequate basic services, despite having extraordinary blessings.

There is some modest progress. But at the end of the day, the country is not what we hoped it would be.

And then the source of greatest pride really is what our young men and women in uniform and our coalition and Iraqi partners and our diplomatic, intelligence and development partners did during the surge in Iraq.