Between 1961 and 1971, the U.S. military spread about 20 million gallons of herbicide across 4.5 million acres of the Vietnamese countryside, as well as parts of Laos and Cambodia. The devastating mission, dubbed Operation Ranch Hand, used various herbicides in an effort to defoliate the forest, making hidden enemies easier to spot, and to destroy food crops used by the North Vietnamese Army and Viet Cong. Each herbicide was denoted by a specific color and named after the markings on their barrels. Among them, History.com details, there were Agent Green, Agent Purple, Agent Pink, Agent White and Agent Blue. But the most common 55-gallon drum found on military bases was Agent Orange, which came in various strengths and made up about two-thirds of the herbicides spread during the war.

In 1991, veterans of the Vietnam War won a major victory with the passage of the Agent Orange Act, which acknowledged that these powerful herbicides were strongly linked to various cancers and other diseases later in life. The bill authorized special health benefits to those exposed to the chemicals. But the act was interpreted by the U.S. Department of Veterans Affairs to cover only those who spent time on the ground in Vietnam or serving on its river system, excluding “blue water” Navy personnel serving on ships off the coast. Now, reports Quil Lawrence at NPR, a Federal Court has ruled those veterans are eligible for the benefits as well.

Court papers show that the U.S. knew that the herbicides weren’t just harmful to plants at least two years before it stopped using Agent Orange in Vietnam in 1971. The byproduct of the manufacturing process, a dioxin called 2,3,7,8-tetrachlorodibenzo-p-dioxin or TCDD was found in large concentrations in Agent Orange and other herbicides. Dioxins accumulate in fatty tissues, and can last for hundreds or thousands of years, contaminating areas for generations and can lead to cancer even in small doses.

Soon after the war, some veterans began noticing higher cancer rates and other illnesses. In 1979, a group filed a class-action lawsuit against the chemical companies on behalf of 2.4 million service members who were exposed to it. After years of legal wrangling, the Supreme Court validated a $240 million settlement that would go to some sick veterans or their next of kin in 1988. But the exposure to Agent Orange was a lifetime risk, and the government acknowledged that many more veterans would likely develop diseases related to dioxin exposure for decades to come. That led to a 1991 bill which directed the Veteran’s Administration to treat diseases caused by Agent Orange exposure as the result of wartime service, meaning the government would foot the bill for treatment.

In implementing the act, the VA did not require direct evidence of Agent Orange exposure, but worked under the presumption that service personnel who served anywhere in Vietnam were exposed, Charles Ornstein at ProPublica reported in 2015. But there was one catch—veterans had to have literally set foot on Vietnamese soil or sail on its inland waterways, which excluded those serving at sea or at Air Force bases outside the country.

After several years of political pressure, in June 2017, 1,500 to 2,100 troops who served as flight and ground crews for the C-123 aircraft that sprayed Agent Orange were finally added to the benefit roles. But the VA did not relent when it came to the blue water sailors, arguing that there was no evidence of exposure to those at sea, despite recent reports that showed how sailors could have been exposed via their drinking water and laundry.

That’s one reason 73-year-old Alfred Procopio Jr., who served on the aircraft carrier USS Intrepid during the war, filed an Agent Orange claim after he developed prostate cancer and diabetes mellitus.

The VA initially denied him aid because he had not actually set foot on Vietnam, but the Court of Appeals's new ruling found that the 1991 law was intended to cover everyone who served in Vietnam, not just ground troops. “Mr. Procopio, who served in the territorial sea of the ‘Republic of Vietnam,’ is entitled to [the law's] presumption. We find no merit in the government's arguments to the contrary,” the 9-2 decision reads.

“The government's foot-on-land requirement, first articulated in 1997, does not provide a basis to find ambiguity in the language Congress chose,” Judge Kimberly Moore ruled in the majority opinion.

Lawrence at NPR reports that Congress had taken up the issue before, and a bill to cover the sailors passed the House last year but a Senate bill stalled.

“These Vietnam veterans sacrificed their own health and well-being for the good of the country, and the benefits that Congress provided — and which the court’s decision now secures — are part of the debt of gratitude we owe them for their service,” Mel Bostwick, one of Procopio’s attorneys said in a statement, reports Ann E. Marimow at The Washington Post.

Nikki Wentling at Stars and Stripes reports that the VA could appeal the decision to the Supreme Court, but there’s no indication yet what the agency will do.

Ornstein at ProPublica reported some 650,000 veterans had made Agent Orange claims at the time of his 2015 reporting. It’s estimated that the new change will make 50,000 to 70,000 additional veterans eligible for Agent Orange benefits.

Veterans and their offspring— whom research indicates may also have been put at risk by their parent’s exposure—are not the only ones suffering from the long-lasting contaminant. On study estimates that 2.1 to 4.8 million Vietnamese people were directly exposed to the chemical during the war. The compound has lingered in the countryside ever since, making its way into food and water, which has caused a multi-generational health crisis and an environmental catastrophe that is still unfolding to this day.