I think Trump said a number of things, not necessarily consistent, on the subject of Iraq.

"Look at the war in Iraq and the mess that we're in. I would never have handled it that way. Does anybody really believe that Iraq is going to be a wonderful democracy where people are going to run down to the voting box and gently put in their ballot and the winner is happily going to step up to lead the county? C'mon. Two minutes after we leave, there's going to be a revolution, and the meanest, toughest, smartest, most vicious guy will take over. And he'll have weapons of mass destruction, which Saddam didn't have.

What was the purpose of this whole thing? Hundreds and hundreds of young people killed. And what about the people coming back with no arms and legs? Not to mention the other side. All those Iraqi kids who've been blown to pieces. And it turns out that all of the reasons for the war were blatantly wrong. All this for nothing!"

http://www.esquire.com/news-politics/interviews/a37230/donald-trump-esquire-cover-story-august-2004/

I don't think he has interest in defending the US action in Iraq.

Consider Iraq. After each pounding from U.S . warplanes, Iraq has dusted itself off and gone right back to work developing a nuclear arsenal. Six years of tough talk and U.S. fireworks in Baghdad have done little to slow Iraq’s crash program to become a nuclear power. They’ve got missiles capable of flying nine hundred kilometers—more than enough to reach Tel Aviv. They’ve got enriched uranium. All they need is the material for nuclear fission to complete the job, and, according to the Rumsfeld report, we don’t even know for sure if they’ve laid their hands on that yet. That’s what our last aerial assault on Iraq in 1999 was about. Saddam Hussein wouldn’t let UN weapons inspectors examine certain sites where that material might be stored. The result when our bombing was over? We still don’t know what Iraq is up to or whether it has the material to build nuclear weapons. I’m no warmonger. But the fact is, if we decide a strike against Iraq is necessary, it is madness not to carry the mission to its conclusion. When we don’t, we have the worst of all worlds: Iraq remains a threat, and now has more incentive than ever to attack us.


In August 2004 Trump turned loud and vocally against the war in an interview with Esquire, more than a year after it started and it was clear after the initial successes an insurgency was developing.

https://www.buzzfeed.com/andrewkaczynski/trump-on-there-being-zero-proof-he-opposed-iraq-before-the-w?utm_term=.yiMNkeVBJJ#.feDxremY55

...

That's the problem.