[Ed. – This presumably won’t make a difference to Trump fans, of course.]
None of the campaigns bothered to check Trump’s own writings, but Andrew Kaczynski of Buzzfeed did, Trump Wrote Iraq WMDs Were Threat Year Before Bush Took Office (emphasis added):
[In] his 2000 book, The America We Deserve Trump noted Iraq was developing weapons of mass destruction and targeted Iraq strikes had little impact on their overall capabilities. The Donald said the best course might be against Iraq to “carry the mission to its conclusion.”
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.
That was 2000. Before Bush took office. Before Bush possibly could have “lied” about Saddam and WMD. And Trump was arguing not only that intervention might be necessary, but that if it happened, it needed to go all the way.