In 2015 Operation Avarice was declassified and it was discovered that there were stockpiles of rockets and warheads containing chemical agents in Iraq. Bearing that in mind, Saddam Hussein was a despot who had nuclear ambitions, was still developing nuclear technology , and planned to see these ambitions through once U.N. sanctions were lifted. Saddam had already used chemical weapons on his own people and had had some notable ties with Islamic fanatics in the past.
While the information leading up to the Iraq war was poor and inaccurate, the motivations behind the war were justified. At least, the motivations of the American people were justified. We did not wish to have another attack allowed on our soil, so we chose to wage war on who we believed to be the enemy.
The Iraq war was not justified for a couple of reasons. First, sending of troops by a multi country coalition was based on scant evidence at best. Second, we have no business being there in the first place. Once again, the United States is tried to impose its cultural will on another country with disastrous results. How about we mind our own business for a change?
In hindsight, the Iraq War was not justified. The Iraq War was pitched to the American people on two fronts: first, eliminate Saddam Hussein's cache of weapon's of mass destruction, and second, combat terrorism. After we invaded we found that the intelligence we had was incorrect, and Iraq did not have weapon's of mass destruction. Furthermore, the terrorist threat was in Afghanistan, rather than Iraq. Thus, the war appears to have been unjustified.
No, the Iraq War was not justified. Instead, our government decided to go there and engage in the war based on false information about the presence of weapons of mass destruction. What we have been left with is a region that is now so unstable that terrorists have taken over. Our actions in starting that war has led to the current mess with ISIS in the Middle East.