The National Union of Mineworkers (NUM) was once the most powerful in the UK, boasting around 500,000 members.
Arthur Scargill was an official from the Yorkshire area of the NUM
But with the decline of Britain's once strong mining industry - especially after the bitter 1984 Miners' Strike - the union saw its membership dwindle.
It is now at a point where it is considering merging with Rail
Maritime and Transport union (RMT).
The union's influence was at the core of the Labour Party in the early years of the 20th century, when more than 600,000 mineworkers toiled to provide coal for Britain's industrial might.
The NUM formed in 1945, as British industry prepared to bounce back from wartime, nationalising its coal industry.
In the 1960s, industrial disputes were often dealt with without the need for strike action.
But a more militant attitude became apparent in the NUM's dealings towards the end of the 1960s.
The 1984 strike saw bloody clashes between police and strikers
In 1974, during Britain's decade of industrial dispute, a coal miners' strike brought Ted Heath's Conservative government of the day to its knees, after the country was forced to adopt three-day working weeks to save energy.
Heath's Tory successor Margaret Thatcher, five years into her stride as prime minister in 1984, was not about to let the same thing happen to her after outlining plans to close down many of Britain's pits.
But Mrs Thatcher faced an equally forthright opponent in Arthur Scargill, the Yorkshireman who as president had led the union since 1981.
In that year, the Yorkshire NUM held a ballot in which its 66,000 members voted for strike action if any pit was threatened with closure "unless on grounds of exhaustion".
This issue was used by Mr Scargill as the cornerstone for calling a strike without holding a national ballot - the first time ever in the union's history.
At the time of the strike, coal miners were among the highest-paid industrial workers in the country. They were also often asked to support other workers seeking higher wages.
Mr Scargill was confident he could take on Mrs Thatcher's government and inflict the same kind of damage the union had a decade earlier.
The number of miners has dropped sharply over the past 20 years
But the government had been prepared for a clash with the miners and had stockpiled coal and oil.
The strike began after workers at the Cortonwood pit near Barnsley walked out after being told their mine was scheduled for closure.
The union's executive tried to call a national ballot a month later, but it was over-ruled by Mr Scargill.
But the union saw a breakaway faction emerge during the industrial dispute, when miners in Nottinghamshire voted by three-quarters to oppose the strike and form the breakaway Union of Democratic Mineworkers.
Flying pickets of mineworkers sent to stop deliveries leaving from mines were met by ranks of baton-wielding riot police.
The hot summer weather during the early stages of the 1984 strike meant Britain did not suffer a second Winter of Discontent.
A compromise deal reached between the National Coal Board and the NUM in September of that year was over-ruled by Mr Scargill. By that stage, many impoverished miners were crossing the picket lines.
Many of the NUM's members chose to strike over threatened pit closures
As the strike stretched through Christmas, the NUM realised the strike was not working.
In March 1985, its executive voted 98 to 91 to allow miners back to work.
Though they returned to their collieries between union banners and pit brass bands, many realised their jobs were numbered. Pit closures began the year after, decimating the industry.
The once-powerful union - which led Tory prime minister Stanley Baldwin to once say "you do not rub your nose against the NUM" - became a shadow of its former self.
Critics say the NUM had been singled out as a target for Mrs Thatcher's desire to break unions, while others say Mr Scargill's insistence on not holding a ballot sounded a death knell to a once proud union.
The Labour Party leader of the time, Neil Kinnock, criticised Mr Scargill, saying he was responsible for the striking miners' situation.
Currently led by union national secretary Steve Kemp from offices in Barnsley, the merger talks could spell the end of an important player in British industrial relations.
But the leader of the RMT, Bob Crow, believed a merger with his union, if it went ahead, would make sense.
"We have always had a close relationship with the miners both politically but more importantly industrially because our members have always carried coal," Mr Crow said to BBC News Online.