Process Blog Home

Tear Gas and the U.S. Border

Four coughing Vietnamese women and children emerge from a thicket, observed by four armed American soldiers.

In Thu Xuan, South Vietnam, US soldiers use tear gas to “flush” women and children from hiding, February 12, 1966. Photo by Steve Van Meter/UPI, via Manhhai on Flickr.

Many Americans spent the last hours of Thanksgiving weekend glued to the television. They were not watching football, however. They were watching footage of migrants at the United States–Mexico border fleeing from tear gas. Although this incident near San Diego was not the first time such chemical weapons have been used at the border, the clouds of gas followed the massing of over 5,000 U.S. soldiers along the border. Yet it was not soldiers who unleashed tear gas. Instead, it was Customs and Border Protection. To understand why a civilian law-enforcement agency came to use tear gas requires looking at the weapon’s history. Like what happened at the border, tear gas was widely used for purposes beyond riot control during the U.S. war in Vietnam.

First, a clarification: the term “tear gas” conflates multiple different chemicals. The recent border deployment included OC (the key ingredient in “pepper spray”), obscuring smoke, and mainly CS, the most common form of tear gas today. Ben Corson and Roger Stoughton, whose surnames form its appellation, first formulated CS in 1928. The U.S. military adopted CS in 1959 and eventually phased out other comparable agents in mid-1963. When CS first became available, it was sometimes called a “super tear agent” to distinguish it from other compounds.

The effects of CS are intense. It makes the eyes tear profusely and close involuntarily. It also induces coughing, chest tightness, and difficulty breathing. Mucus flows, and many people vomit, or even expel urine or excrement. Direct skin exposure to CS can be painful, and made worse by moisture, such as sweat, leading to blisters and burns. The name “tear gas” is misleading because CS causes much more than tears. And, it must be said, CS is not a gas. It is a fine powder.

In March 1965, when U.S. newspaper headlines first revealed “gas” use in South Vietnam, President Lyndon Johnson’s staff acted quickly to alleviate public concerns. Some accused the United States of deploying banned chemical weapons. After World War I, marked by heavy deployment of chemical weapons that killed or maimed thousands of soldiers, a 1925 international agreement, the Geneva Protocol, outlawed the use of asphyxiating or otherwise poisonous chemicals. Forty years later, the Secretaries of State and Defense, along with Johnson, tried to make clear that the United States had not used these types of weapons in Vietnam. Instead, the chemicals were mere “tear gas.”

The United States did not ratify the Geneva Protocol, but Washington claimed to adhere to it. Adherence in 1965 entailed using chemicals that were not asphyxiating but instead “irritating.” Another ambiguous term floated at the time was “nonlethal,” still widely used today. One further term experts adopted was “riot control agents,” but this term raised a question in 1965 that is equally applicable to the U.S.–Mexico border today: was there a riot?

Secretary of State Dean Rusk insisted that no “military gases” had been used in South Vietnam, only riot control agents. Johnson himself saw no cause for alarm because these agents were what the police in Washington, D.C. would use in case of a riot. CS, however, was not available yet to police. Army and National Guard units operating domestically received authorization to disperse CS only twice prior to its introduction in South Vietnam, in Mississippi in 1962 and Maryland in 1964 to break up crowds.

But rioting did not spur the earliest military use of CS in South Vietnam, in combined operations of U.S. and local forces. Instead, the chemical was released in situations where guerrillas and U.S. personnel were intermingled and conventional weapons might kill both. Soon, however, the most common use of CS came not in the setting of mingled friend and foe, nor even in riot control.

Instead, CS was used for two primary combat purposes. One was to “flush” people out of hiding. A key challenge for the United States during its war in Vietnam was simply locating the “enemy.” CS, whose effects were so unpleasant, was supposed to force people out of hiding. Whether in heavy undergrowth or in tunnels and bunkers, the U.S. military used CS to force people out into the open. In many cases, they were then killed with airstrikes, artillery, or conventional gunfire. CS made targeting otherwise hidden people easier. The second purpose was to control access to terrain. New formulations of CS were developed that could be persistent and even water-resistant, meaning they could contaminate buildings, bunkers, tunnels, and landscapes for weeks or longer. Or, to keep people away from a given location, CS would be used to create a barrier. We should keep this legacy in mind today, as law-enforcement agencies on borders from Ceuta to Gaza to San Diego deploy tear gas.

Surprisingly, the U.S. military no longer uses CS in combat operations due to regulations and international law. These resulted from public outcry against CS, which only intensified after news reports initially revealed its use in South Vietnam.

In 1969, President Richard Nixon triangulated among the antiwar movement, critics in Congress, and the Soviet Union by committing to a policy of no first use of chemical weapons. But CS was excluded. Six years later, however, President Gerald Ford responded to antiwar sentiment social movements, scientists, and Congress expressed by issuing an executive order banning the military use of “riot control agents” and herbicides in combat, except under special circumstances. The 1993 Chemical Warfare Convention superseded the Geneva Protocol to outlaw chemical weapons in war, and the United States ratified it in 1997. This agreement expressly did not cover domestic law-enforcement use of “riot control agents.” As a result, the U.S. military would continue to uphold Ford’s executive order while civilian law enforcement remained unfettered. This legal situation conditioned contemporary deployments, from Ferguson, Missouri, to San Diego, California.

Writing for The Nation earlier in November, journalist Ryan Harvey quoted documents from the Defense Department that indicated President Donald Trump’s 2018 military mission on the border would include “terrain denial.” But the military could not legally deploy CS to deny terrain. Instead, civilian officers were the ones to release CS on the border. In a situation where there was no riot, a civilian agency mimicked U.S. military practice of prior decades to control terrain and enforce a border.

Today, the U.S.–Mexico border near San Diego is marked by a hardened fence, concertina wire, U.S. officers, Mexican police, train tracks, and a canal, which together make unauthorized crossing impossible. The clouds of CS denied migrants the space of protest. These chemical weapons came from the U.S. side but affected civilians on the Mexican side, including children, who are at particular risk of deleterious health consequences from exposure.

There was no riot. Even as a few frustrated migrants tossed rocks or other projectiles toward the border zone, footage shows those actions to have been a response to the gas Border Patrol officers unleashed. Denied the terrain, denied entry, asylum-seekers were also denied the safety they sought. But CS did not deny their humanity. Instead, it weaponized it, attacking their skin, their eyes, and their mucus membranes.

Four decades ago, organized condemnation of CS pushed a presidential administration to outlaw its use by the U.S. military. Social movements today might heed this example. Regulations could remove CS from the arsenal of Customs and Border Protection, but such restrictions will not crystallize from thin air. Instead, unlike the fleeting clouds of CS, a movement against such chemical weapons will have to be firm, persistent, and concrete.

Further Reading:

Sarah Bridger, Scientists at War: The Ethics of Cold War Weapons Research (Cambridge, MA: Harvard University Press, 2015).

D. Hank Ellison, Chemical Warfare during the Vietnam War: Riot Control Agents in Combat (New York: Routledge, 2011).

Anna Feigenbaum, Tear Gas: From the Battlefields of World War I to the Streets of Today (New York: Verso, 2017).

Stuart Schrader, Badges Without Borders: How Global Counterinsurgency Transformed American Policing (Oakland: University of California Press, forthcoming).

Stuart Schrader is a Lecturer at Johns Hopkins University, teaching courses on the carceral state, African American social movements, and critical race theory. He is the author of a forthcoming book from University of California Press, Badges Without Borders: How Global Counterinsurgency Transformed American Policing, from which this article draws.

Recent Posts

2024 JAH African American History …


On “The U.S. Culture Wars Abroad: Li …


What’s in the December Issue of the …


(Trans)American History across Borders