Margaret Thatcher secretly considered calling out the troops at the height of the miners' strike amid fears union action could destroy her Conservative government, according to newly released files.
Government papers from 1984, released by the National Archives, show ministers were so concerned at the outbreak of a national docks strike while the miners were still out, they considered declaring a state of emergency.
Plans were drawn up for thousands of service personnel to commandeer trucks to move vital supplies of food and coal around the country.
It was probably the closest Mrs Thatcher came to defeat in her battle with the miners but the scheme was never implemented after the dockers' action petered out after less than two weeks.
The epic, 12-month confrontation between the Conservative government and the National Union of Mineworkers (NUM) and its left-wing president Arthur Scargill was one of the defining episodes of the Thatcher era.
It saw some of the worst industrial violence the country had witnessed, with hundreds injured in brutal picket line clashes between police and miners, and ended in crushing defeat for the NUM.