How does the government justify the war with Iraq?

So, Donald Rumself and the Reagan Administration provided weapons to Saddam and no one cared when he used them on other countries and his own people. Then, when we invaded we said he was using weapons on his own people. Well we already knew that right? Then theres the whole connection with 9/11 which Iraq had nothing to do with, so why invade? And the CIA trained Osama Bin Laden. Bush said we went to war with Iraq because they had WMD, which they didn't. And if they did they were provided by the US anyway. So that makes no sense. And in Bush's address telling Saddam he had 48 hours to leave, he said the war was directed at the terrorists and such and not the innocent people. Is that why we bomb civilians? I know the real reasons for the war like it was planned long before Bush came into office. I'm just interested in the government's reasoning and arguments. Feel free to say anything.