US Navy Chemical Warfare film from the 50s
 

Sure it's dated, and with that usual "gee whiz" 50's optimism? But the numerous means of delivery systems?

Wonder how many either a) got dusted off for the Twilight War, or b) were improved with 90s tech, then used?

https://warisboring.com/u-s-navy-fil...453#.nr6dib731

Has anyone actually used these in a campaign at all?

Hard to say really, according to the U.S. Army Chemical Materials Activity (CMA) 45% of the US's stockpile of chemical weapons were destroyed by 2007

In 1986, President Ronald Reagan made an agreement with Chancellor Helmut Kohl to remove the U.S. stockpile of chemical weapons from Germany. As part of Operation Steel Box, in July 1990, two ships were loaded with over 100,000 shells containing GB and VX taken from U.S. Army weapons storage depots such as Miesau and then-classified ammunition FSTS (forward storage/transportation sites) and transported from Bremerhaven, Germany, to Johnston Atoll in the Pacific, a 46-day nonstop journey - Broadus, James M., et al. The Oceans and Environmental Security: Shared U.S. and Russian Perspectives, p. 103, Island Press, 1994.

My guess their are plenty of weapons stockpiled in the US and the US might start looking into updating their delivery means as soon as the shooting starts. I doubt that US would use them first though.