Iraq used chemical weapons in the Iran-Iraq war: https://en.wikipedia.org/wiki/Iraqi_chemical_weapons_program
Israel used white phosphorous till 2013: http://www.bbc.com/news/world-middle-east-22310544
the Soviet Union was accused of using chemical weapons in afghanistan: http://www.paulbogdanor.com/left/afghan/report.pdf
The UN stated that Cuban units used VX as well as Sarin: https://en.wikipedia.org/wiki/Chemical_warfare#Angola
even the vietnamese used chemical weapons: https://en.wikipedia.org/wiki/Vietnamese_border_raids_in_Tha...
None of these examples include the use of chemical weapons in WWII or WWI. During these wars most major european countries used chemical weapons of some kind.
these instances don't excuse their usage, But I don't believe much is gained by pretending the rest of the world is blameless.
Hiroshima and Nagasaki: 129-226k dead
Nazi Holocaust: 4.9-11m dead
Soviet Holodomor: 1.8-7.5m dead
Cambodian Genocide: 1.7-3m dead
Armenian Genocide: 800k-1.5m dead
Vietnam War (all deaths, US period): 1-3m dead
In terms of human death, WMDs have historically been the least of conflict-affected people's worries, compared to starvation and drawn out total war.
It may not be "the international community", but it is certainly not just Trump. South Korea, China, and lately Japan all have an interest and are actively attempting to steer results.
I mean, I'd bet if you consult your model of Trump that you think is acting it will tell you that being a crazy madman unconstrained by rationality or morality he unilaterally nuked Pyongyang last month. That model applied consistently, instead of piecemeal whenever cynically convenient, is clearly not predictive. (If that is not your personal model, timthelion, I am sure this message reaches many people for whom that is their unexamined model, so still not a waste.)