During the First World War the coal industry was nationalised by the government. Coal was at the heart of British industry and was even more important than other energy sources - such as electricity and petrol - that emerged in the 1920s. This was the reason government took-over the mines during the war.
Under government control, wages, hours and safety improved, and at the end of the war miners wanted to retain the status quo. Sir John Sankey led a Commission to investigate this issue, and recommended that nationalisation should continue. The Prime Minister, David Lloyd George, refused; the mine owners were influential and powerful and he wanted to avoid taking control of an industry facing serious conflict. Lloyd George returned the mines to the mine owners in 1921.
Conditions in the coal mining industry were very hard indeed, and partly due to this, mineworkers were some of the most heavily unionised and most militant workers.
In the aftermath of the First World War the coal industry was under pressure from foreign competition. As a result, in 1920, mine owners demanded cuts in wages and an extended working day stating that the alternative would be complete closure of the least economically viable pits. The miners refused to accept these measures.
A further cause of tension was the threat of the mine owners to impose pay cuts and increase working hours when the coalmines were returned to private ownership and out of government control on 31 March 1921. The miners were told they had to accept the new conditions or lose their jobs. They called on the railwaymen and transport workers to join them in a strike starting on 15 April 1921. Together these three unions formed the Triple Alliance.
The railwaymen and transport workers felt that the miners had not tried hard enough to negotiate. On the day the strike was supposed to begin they withdrew their support. This became known as 'Black Friday', and although the miners continued with a bitter strike they were eventually forced back to work after accepting a wage cut.
On 30 June 1925, with one month's notice, the mine owners announced that existing working conditions would end. A new demand was made, involving a further cut in wages and an extra hour on the working day. However, the new miners' leader, A.J. Cook, was firm in his view that they would accept 'Not a penny off the pay, not a minute on the day'.
A lockout seemed likely, but this time the Triple Alliance held together, threatening a complete embargo on all production or movement of coal, which would have brought the country to a halt. The Trades Union Congress (TUC) wanted to help the miners, but also wanted to involve the government in the dispute in the hope government involvement would bring a lasting settlement.
The Conservative Prime Minister, Stanley Baldwin, agreed to pay mine owners a subsidy which would avoid the wage cut for miners. This success became known as 'Red Friday'. However, the agreement was only for 9 months and the government took no responsibility for running the mines. It seemed that conflict would arise again once the subsidy ended. Baldwin was buying time. He set up the Samuel Commission to study the coal industry and report back. He also set up the Organisation for the Maintenance of Supplies (OMS) in 1925. This established a force of volunteers to drive public transport in the event of a strike. The OMS also set up stores of food and fuel.
Between 1921 and 1925 relations between Labour and the trade union movement, and government and employers got steadily worse. Many areas of British industry were going through a disastrous slump, and during the war British industry had lost many of its old markets to American and Japanese competition. The industries that were particularly hard hit were the old 'staple' industries - shipbuilding, coal and textiles. These industries relied heavily on export markets that were disappearing fast.
From the unions' point of view, the staple industries were large-scale employers, which made a bad situation for the miners even worse. Employers were trying to cut costs, starting with wages. Dockers, railway workers, builders and many others all had to take wage cuts, and to defend their members, unions drew closer together. In 1921 Ernest Bevin, the leader of the powerful Transport and General Workers Union (TGWU), convinced the Trades Union Congress (TUC) to create a General Council (TUC). Its role was to coordinate a major strike if this became necessary.
In 1925 Britain returned to the gold standard. This was a way of protecting the value of the pound against foreign currency, particularly the dollar. However, it depressed the economy and made British exports more expensive, which in turn, made the rising unemployment of the 1920s worse.
Throughout 1925 and 1926 tension increased with government and the mine owners on one side and the unions on the other. In March 1926 a Royal Commission headed by Sir Herbert Samuel recommended small wage cuts, but not longer hours. These recommendations were not acceptable to the miners or the employers. The Trades Union Congress (TUC) General Council (TUC) threatened a strike of key workers on 4 May.
Printers at the Daily Mail newspaper refused to print a leading article criticising the Trades Union Congress (TUC). For the government, this action was unacceptable. All attempts at negotiation were broken off and the General Strike began on 4 May. The coal mine owners declared all strikers were locked out - and out of a job.