article_snippet: Here are nine things to know about these chemical weapons and how we got here: .
article_snippet: April 22 marks the 100th anniversary of the first use of chemical weapons in modern warfare at Ypres in Belgium.
article_snippet: Huge production: From World War I to 1968, the United States produced nearly 40,000 tons of chemical weapons.
article_snippet: Huge production: From World War I to 1968, the United States produced nearly 40,000 tons of chemical weapons were either nerve agents or blister agents.
article_snippet: Into the sea: From 1967 to 1970, the U.S. Army disposed of thousands of chemical warfare agents and ammunition into the sea as part of Operation Cut Holes and Sink 'Em (CHASE).
article_snippet: Date of destruction: In 1997, the United States ratified the Chemical Weapons Convention Treaty and agreed to destroy all of the United States chemical weapons by April 29, 2012.
highlights_snippet: Here are nine facts to know about chemical weapons .