Off the top of my head, we backed Iraq in the Iran/Iraq war, as the lesser of two evils.
The main suppliers of dual-use technology & weapons were the Germans & French, IIRC.
A review of thousands of declassified government documents and interviews with former policymakers shows that U.S. intelligence and logistical support played a crucial role in shoring up Iraqi defenses against the "human wave" attacks by suicidal Iranian troops. The administrations of Ronald Reagan and George H.W. Bush authorized the sale to Iraq of numerous items that had both military and civilian applications, including poisonous chemicals and deadly biological viruses, such as anthrax and bubonic plague.
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