The U.S. Army [will have] destroyed about 90 percent of its aging chemical weapons after it wraps up work this week in Utah, where it has kept its largest stockpile - a witches' brew of toxins, blister and blood agents that accumulated through the Cold War. The Army's Deseret Chemical Depot in Utah's west desert burned its last hard weapons in a 1,500-degree furnace on Wednesday. The depot ... at its peak held some 13,600 tons of chemical agents, making it the world's largest. The U.S. is part of an international treaty to rid the world of chemical weapons, a campaign taking place with spotty success around the globe. The goal was supposed to be accomplished by April 29 but will take years longer. The U.S. has acknowledged it will take as long as 2021 to finish destroying the final 10 percent of its chemical weapons. Russia is farther behind in its effort, having destroyed only about 48 percent of a large cache of chemical weapons. Chemical weapons were introduced into warfare during World War I, killing 90,000 troops on battlefields, according to the Organisation of for the Prohibition of Chemical Weapons.

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