Iraq and Iran fought a horrific war from 1980 to 1988. Saddam Hussein was unquestionably the perpetrator. He repeatedly used chemical weapons against Iranian troops, then in 1988 he attacked the Kurdish village of Halabja, in northern Iraq, with mustard gas, killing thousands of civilians.
The president of the United States was conservative demi-God Ronald Reagan:
In 1983, President Reagan sent a special envoy to Baghdad. He was Donald Rumsfeld, and that visit resulted in the now famous picture of Rumsfeld shaking hands with Saddam Hussein. This was in December of 1983. This was at a time when the US was secretly aware that Iraq was using chemical weapons against the Iranians almost daily. There's evidence that the battlefield intelligence provided to Iraq helped the Iraqis better calibrate their gas attacks against the Iranians. Around this time, the administration concluded that Iraq's defeat in the war would be contrary to US interests in the Persian Gulf. The economic aid to Iraq started in 1983, and by the end of the war amounted to more than a billion dollars. . . .Just so you know.
Near the end of the war when Saddam Hussein used chemical weapons against his own citizens, the Kurds. We know a great deal about this now. At the time, the United States prevented a move in the UN to impose economic sanctions against Iraq, saying that the sanctions would be useless or counterproductive. So in effect, the United States defended Saddam Hussein's use of chemical weapons even as late as 1988, and this kind of a relationship continued through the Reagan administration and into the first President Bush administration until the very day that Iraq invaded Kuwait in early August 1990.