LONDON — As striking miners challenged her grip on power in 1984, Prime Minister Margaret Thatcher secretly considered calling out the British military to transport vital supplies of food and coal around the country and declaring a state of emergency to bolster the government in one of the defining confrontations of her tumultuous years in office, according to previously classified documents released on Friday.

The government papers, released by the National Archives, cast new light on an era that shaped Britain for decades, crushing the power of labor unions and establishing an ideological reverence for market forces that has endured through successive Labour and Conservative governments.

In 1984, by contrast, Mrs. Thatcher, who died last April at age 87, faced a militant union movement that threatened to bring the country to a halt as dockworkers seemed poised to support the striking coal miners who clashed frequently with the police along the picket lines.

The miners’ leader, Arthur Scargill, declared the strike to be a “social and industrial Battle of Britain,” evoking the epic contest with Nazi Germany in World War II. At the same time, Mrs. Thatcher’s Conservative government saw the strike, which began in March 1984, as an opportunity to break militant unions once and for all.