BOQUILLA, MEXICO – The farmers armed themselves with sticks, rocks and homemade shields, ambushed hundreds of soldiers guarding a dam and seized control of one of the border region’s most important bodies of water.

The Mexican government was sending water — their water — to Texas, leaving them next to nothing for their thirsty crops, the farmers said. So they took over the dam and have refused to allow any of the water to flow to the United States for more than a month.

“This is a war,” said Victor Velderrain, a grower who helped lead the takeover, “to survive, to continue working, to feed my family.”

The standoff is the culmination of long-standing tensions over water between the U.S. and Mexico that have recently exploded into violence, pitting Mexican farmers against their own president and the global superpower next door.

Negotiating the exchange of water between the two countries has long been strained, but rising temperatures and long droughts have made the shared rivers along the border more valuable than ever, intensifying the stakes for both nations.

The dam’s takeover is a stark example of how far people are willing to go to defend livelihoods threatened by climate change — and of the kind of conflict that may become more common with increasingly extreme weather.

Along the arid border region, water rights are governed by a decades-old treaty that compels the U.S. and Mexico to share the Colorado and Rio Grande rivers, with each side sending water to the other. Mexico has fallen far behind on its obligations to the U.S. and is now facing a deadline to deliver the water this month.

But this has been one of the driest years in the past three decades for Chihuahua, the Mexican border state responsible for sending the bulk of the water Mexico owes. Its farmers have rebelled, worried that losing any more water will rob them of a chance for a healthy harvest next year.

“These tensions, these tendencies, are already there, and they’re just made so much worse by climate change,” said Christopher Scott, a professor of water resources policy at the University of Arizona. “They are in a fight for their lives, because no water, no agriculture; no agriculture, no rural communities.”

Since February, when federal forces first occupied the dam to ensure water deliveries to the U.S. continued, activists in Chihuahua have burned government buildings, destroyed cars and briefly held a group of politicians hostage. For weeks, they’ve blocked a major railroad used to ferry industrial goods between Mexico and the United States.

Their revolt has alarmed U.S. farmers and politicians. Texas Gov. Greg Abbott appealed to Secretary of State Mike Pompeo last month, demanding that he persuade Mexico to deliver the water by the deadline this week or risk inflicting pain on U.S. farmers.

Mexican President Andrés Manuel López Obrador, who has repeatedly bent to President Donald Trump’s demands on immigration, has vowed that his country will make good on its water obligations to the U.S. — whether the state of Chihuahua likes it or not.

He sent hundreds of National Guard members to protect Chihuahua’s dams, and his government temporarily froze bank accounts belonging to the city where many of the protesters live.

For farmers, the government’s stance is a betrayal.

Velderrain, 42, said he never saw himself as the type of person who would lead hundreds over a hill to overwhelm a group of soldiers protecting a cache of automatic weapons. But there he was in a video posted on Facebook, escorting a Mexican general out of the Boquilla Dam on the day he led the takeover.

Surprised and heavily outnumbered, the National Guard quickly surrendered. Later that day, one protester was shot and killed by the National Guard.

“We have always dedicated ourselves to work; we’ve never been known as protesters,” Velderrain said back on his farm. “What happened at the Boquilla dam was impressive, because we took off our farmer clothes and put on the uniform of guerrilla fighters.”

The federal government argues that the protesting farmers are also hurting other Mexicans by preventing water from flowing to their compatriots downstream and that the growers would still have access to at least 60% of the water they need for next year.

“Agriculture, like any other profession, has risks,” said Blanca Jiménez, head of Mexico’s National Water Commission. “One of the risks is that there are years when it rains more and years when it rains less.”