The Chemical Warfare Service was established on 28 June 1918, combining activities that until then had been dispersed among five separate agencies of the United States federal government.

A letter to the War Department dated 5 April 1862 from New York City resident John Doughty proposed the use of chlorine shells to drive the Confederate Army from its positions.

[1] The earliest predecessors to the United States Army Chemical Corps owe their existence to changes of military technology early in World War I.

[2] By 1917, the use of chemical weapons by both the Allied and Central Powers had become commonplace along the Western, Eastern and Italian Fronts, occurring daily in some regions.

[3] In 1917, Secretary of the Interior Franklin K. Lane, directed the Bureau of Mines to assist the Army and Navy in creating a gas war program.

[2] Researchers at the Bureau of Mines had experience in developing gas masks for miners, drawing poisonous air through an activated carbon filter.

[2][4] Manning recruited chemists from industry, universities, and government to help study mustard-gas poisoning, investigate and mass-produce new toxic chemicals, and develop gas-masks and other treatments.

[6] Additional War Department orders established a Chemical Service Section that included 47 commissioned officers and 95 enlisted personnel.

[13] In the interwar period, the Chemical Warfare Service maintained its arsenal despite public pressure and presidential wishes in favor of disarmament.

[18] In 1943 a U.S. ship carrying a secret Chemical Warfare Service cargo of mustard gas as a precautionary retaliatory measure was sunk in an air raid in Italy, causing 83 deaths and about 600 hospitalized military victims plus a larger number of civilian casualties.

Following the Battle of Tarawa, during which the U.S. forces suffered more than 3,400 casualties in three days, CWS chief Major General William N. Porter pushed superiors to approve the use of poison gas against Japan.

[20] Along with that he was the Hawaii Territorial Coordinator for Civilian Gas Defense and Joint service Pacific theater chief chemical warfare officer under Adm. Nimitz.

[17] With the change came the added mission of defending against nuclear warfare, in addition, the corps continued to refine its offensive and defensive chemical capabilities.

[22] North Korea, the Soviet Union and China leveled accusations at the United States claiming the U.S. used biological agents during the Korean War; an assertion the U.S. government denied.

Two CCIA staff members again toured selected U.S. intelligence agencies in Japan, Korea, Okinawa, Taiwan, the Philippines, and Hong Kong in the third quarter of financial year 1962.

The U.S. and its allies officially argued that herbicides and defoliants fell outside the definition of "chemical weapons", since these substances were not designed to asphyxiate or poison humans, but to destroy plants which provided cover or concealment to the enemy.

The Chemical Corps continued to support U.S. forces through the use of incendiary weapons, such as napalm, and riot control measures, among other missions.

As the war progressed into the late 1960s, public sentiment against the Chemical Corps increased because of the Army's continued use of herbicides, criticized in the press as being against the Geneva Protocol; napalm; and riot control agents.

A 1969 incident, in which 23 soldiers and one Japanese civilian were exposed to sarin on the island of Okinawa, while cleaning sarin-filled bombs, created international concern while revealing the presence of chemical munitions in Southeast Asia.

[29] When the U.S. BW program ended in 1969, it had developed seven standardized biological weapons in the form of agents that cause anthrax, tularemia, brucellosis, Q-fever, VEE, and botulism.

[27] Recruitment and career advancement was halted and the Chemical School at Fort McClellan was shut down and moved to Aberdeen Proving Grounds.

[30] In an effort to hasten chemical defense capabilities the corps restructured its doctrine, modernized its equipment, and altered its force structure.

[30] After Iraq invaded Kuwait in 1990 and much of the world responded by amassing military assets in the region, the United States Army faced the possibility of experiencing chemical or biological (CB) attack.

[33] Large scale drills were conducted in the desert to better acclimatize troops to wearing the bulky protective clothing (called MOPP gear) in hot weather conditions.

[33] Though Saddam Hussein had renounced the use of chemical weapons in 1989, many did not believe he would really honor that during a conflict with the United States and the broader coalition forces.

[36] A 1996 United States Government Accountability Office report concluded that U.S. troops remained highly vulnerable to attack from both chemical and biological agents.

The report blamed the U.S. Department of Defense for failure to address shortcoming identified five years earlier during combat in the Persian Gulf War.

Develop doctrine, equipment and training for CBRN defense which serve as a deterrent to any adversary possessing weapons of mass destruction.

The Chemical Corps branch insignia consists of a cobalt blue, enamel benzene ring superimposed over two crossed gold retorts.

[44][45] Robert S. Mulliken served in the CWS making poison gas during World War I, and he later earned the Nobel Prize in 1966 for his work on the electronic structure of molecules.