Over 20,000,000 U.S. gallons of this and similar agents were dropped in Vietnam to cause deforestation, targeting the resistance food supply and concealment. The Agent Orange has caused, in the most conservative estimate, over 400,000 deaths and 3 million suffering from illnesses or birth deformities due to its toxic composition. Although the alleged intent of the operation wasn't to cause this, it was well known at the time what the consequences would be. Dr. James R. Clary, which worked directly for the Chemical Weapons Branch, says:
When we initiated the herbicide program in the 1960s, we were aware of the potential for damage due to dioxin contamination in the herbicide. We were even aware that the military formulation had a higher dioxin concentration than the civilian version due to the lower cost and speed of manufacture. However, because the material was to be used on the enemy, none of us were overly concerned.
So considering all this and looking at the likes of the Hague Convention and the Geneva Protocol, is there some reason why the use of this chemical agent wasn't considered a war crime?
Source: reddit post