As Margaret Thatcher took office as Britain’s first female prime minister in May 1979, she confronted a nation mired in economic recession.

Businesses were failing, and inflation and unemployment were rising. Thatcher immediately set out to turn the economic situation around, according to her firm belief in the independence of the individual from the state and limited government interference in the economy. Her goal when she took office, she later said, was to turn Britain from a “dependent to a self-reliant society, from a give-it-to-me to a do-it-yourself nation.”

To do this, Thatcher focused on privatizing state-owned industries—such as steel and coal—that relied heavily on government subsidies, as well as curbing the power of Britain’s trade unions. In the 1970s, strikes called by the National Union of Mineworkers (NUM) had caused widespread fuel shortages and brought the country to a screeching halt. Thatcher had seen how the effects of the strikes had taken down the government of the last Conservative prime minister, Edward Heath, and was determined to avoid the same fate.

On the other side of the looming battle over coal was Arthur Scargill, who became president of the National Union of Mineworkers (NUM) in 1981. As leader of the Yorkshire miners during the national strike in 1974, he helped pioneer more radical labor organization tactics (such as sending picketers to specific plants to halt transportation of coal) that made that strike such a success.

On March 6, 1984, the National Coal Board announced its plan to cut the nation’s coal output by 4 million tons, in an effort to stem a $340 million annual loss. At the time, Britain had 170 working collieries, commonly known as pits, which employed more than 190,000 people. Scargill and the NUM estimated the board’s plan would mean the closure of 20 pits and the loss of some 20,000 jobs.

The same day the plan was announced, miners at a colliery in South Yorkshire walked out on the job. Scargill used this as an opportunity to call a nationwide strike against the planned pit closures. Controversially, he never held a national vote within the NUM, and not all miners were on board with the walkout. In some parts of the country, miners kept working, causing tensions with picketing workers who branded them as “scabs.”

Using Scargill’s aggressive picketing tactics, the striking miners managed to shut down many pits across Britain. But unlike in the 1970s, Thatcher had taken steps to stockpile enough coal and coke to keep the country supplied for at least six months in case of a strike. She had also made secret deals with non-unionized drivers to transport the coal, ensuring that power outages would not cripple the country as during previous strikes.

The striking miners faced off against police forces backed by Thatcher’s government, in clashes that often turned violent. The stakes were high on both sides: Scargill compared the strike to Britain’s fight against Nazi Germany, while Thatcher viewed it as an opportunity to crush militant labor unions for good. Documents declassified in 2014 revealed that Thatcher considered calling out the military to transport food and coal, and even declaring a state of emergency in order to strengthen her government’s position.

Some of the worst violence occurred in South Yorkshire, including a standoff at the British Steel coking plant in Orgreave on June 18, 1984 involving 10,000 miners and 5,000 police officers. When the smoke cleared, 51 miners and 72 police officers had been injured in what became known as the “Battle of Orgreave.” Dozens of miners were arrested, but the government’s prosecution of them fell apart after it emerged that the police had fabricated evidence, among other wrongdoings.

As the strike dragged on, Thatcher’s government held firm. Working miners in Nottinghamshire and South Leicestershire started a rival union, the Democratic Union of Mineworkers, and many miners across the country gradually started returning to work.

On March 3, 1985, Scargill and the NUM voted to end the strike after 362 days. Brass bands, parades and colorful flags accompanied many of the miners back to work, as they put a brave face on defeat. There was no settlement, and Thatcher’s government hadn’t made a single concession. The prime minister’s tough stance helped build her enduring reputation as the “Iron Lady”—a nickname given her by the Soviet press in the 1970s. She would lead the Conservative Party to three straight election wins, and would hold office for 11 years, longer than any other British politician of the 20th century.

The failure of the 1984-85 miners’ strike helped revive the British economy, but had major implications for the future of labor unions and coal mining in Britain. Union membership fell from some 40 percent of the nation’s workforce to barely 20 percent, and dropped even lower in the decades to come.

By 1994, when the coal mining industry was finally privatized, Britain had just 15 collieries; when Thatcher died in 2013, only three remained. The miners’ strike, and the devastating impact of coal’s demise, would leave lasting scars on many of Britain’s former mining communities, as well as lingering resentment toward the government and police force that would endure well into the next century.