On May 1, 1890, demonstrations took place around the world at the behest of the Socialist International of left-wing parties.
The main demand was for limiting the working day to eight hours.
Frederick Engels noted that in all of continental Europe "it was Vienna that celebrated the holiday of the proletariat in the most brilliant and dignified manner."
But, he added, even this dramatic revival of the Austrian trade union and socialist movement was "thrown into the shade" by the "most important and magnificent" London May Day march and rally three days later.
What had, in Engels's words, roused the English workers from almost 40 years of slumber to join the great international army?
He pointed his German readers to the previous year's dockers' strike and the founding of the Gas Workers' and General Labourers' Union, which had grown to embrace 100,000 members.
He proclaimed the unionisation of huge numbers of unskilled workers and the fact that they wanted their unions to be led by socialists.
This rise of militant, left-led "new unionism" could be contrasted with the aloofness and conservatism, both industrial and political, of the craft-based unions led by the aristocrats of labour.
Never slow to welcome the contributions of women, Engels also praised the role played by Eleanor Marx-Aveling, daughter of his lifelong collaborator, in raising funds for the dockers, organising a strike of young women workers in Silvertown, representing women gas workers and spreading socialist ideas through the Liberal radical clubs.
Not that the May Day procession and its eight or more rallies in Hyde Park had been free of problems.
In particular, the labour aristocrats who ran London Trades Council wanted to ban socialist organisations from the march and preferred a negotiated eight-hour day (with voluntary overtime) to legislation, while the Social-Democratic Federation had a superior, sectarian attitude towards unions generally and those for the unskilled in particular.
Of course, many of the basic issues in 1890 - working terms and conditions, trade union recognition and so on - remain the same today because we still live and work in a capitalist society.
But others have changed, emerged and come to the fore. This year, as millions of people mark International Workers' Day across the world, the fight against austerity and privatisation, for pensions and public services and against racism and fascism will feature on many banners and in countless speeches.
But so, too, will the vital call for peace instead of imperialist war. Over the past 120 years, millions of working people and their families have died as the imperialist powers strive to assert their control over markets, raw materials, transport routes, governments and whole countries and continents.
Public consciousness even in the oldest imperialist countries such as Britain - let alone in Latin America, Asia or Africa - is probably more anti-imperialist and anti-war than at any time in history.
Freedom and equality for women, too, is an aspiration and demand far more widespread than ever before, although there are many mountains still to climb. Respect and rights for people of different sexual orientation can now be raised in the labour movement in a growing number of countries.
How to stop the capitalist monopolies and their state power imperilling our planet's ecosystem is a question that went unasked on May Days past, when inexhaustible supplies of energy were taken for granted.
International Workers' Day celebrates the gains of the trade union and left-wing movements and proclaims our determination to defend them.
Today in Britain, we have public services, the NHS, pensions, welfare benefits and employment rights to protect and extend.
Although the trades unions have advanced and retreated since 1890, they are bigger, better organised and more deeply entrenched in society today than they were then.
Despite its victories and defeats during the 20th century the cause of socialism has many more adherents now than it had in any period before the second world war.
There are socialist and communist parties in almost every country today, with a wealth of experience from which to draw and learn.
Here is one of the reasons for studying the history of the labour movement.
The limits, failures and betrayals of social democracy cannot be ignored, just as its beneficial reforms for workers and their families should be acknowledged and defended.
The Communist Party's programme, Britain's Road to Socialism, analyses the experience of past Labour governments.
Winning political office in a general election is not the same as achieving state power, although doing so on the basis of mass working-class action would complete an important first stage in the struggle for socialism.
Instead, the low level of revolutionary political consciousness in the British working-class movement has produced Labour Party leaderships that have no commitment or strategy to making deep inroads into the wealth and power of the monopoly capitalists.
Little or no attempt has been made to politicise and mobilise the mass of the people, or to involve them and the labour movement in transforming the state apparatus.
Crucially, the British labour movement has failed to understand and oppose imperialism in its economic, political, cultural and military aspects, including the "special" - ie especially servile - relationship with US imperialism. Similar confusion persists about the monopoly class character of the European Union.
Such muddled thinking about reforms, mass action, the ruling capitalist class, the state and imperialism has allowed every Labour government so far to be derailed by powerful forces within monopoly capital and the state apparatus.
The history of the communist movement is not without its mistakes and crimes either, which is why Britain's Road to Socialism draws up a balance sheet of the first attempts at building socialism in the former Soviet Union and eastern Europe.
Indeed, the programme goes further, renewing and updating the case for socialism and revolution in the 21st century.
Workers will forever be on the same capitalist tread-wheel until they learn from their own history. Trade unions could do much more to organise classes, schools and publications on the history and politics of the labour movement, which would contribute enormously to the consolidation and politicisation of members' class consciousness.
Our movement has the Marx Memorial Library as a splendid resource that deserves more support across the left and the labour movement.
The Communist Party History Group is making its own modest contribution this May Day with the launch of a new "Our History" series of pamphlets. The first four look at Handsworth workers in the second world war, striking women cigar workers in Cardiff, class in the so-called Glorious Revolution of 1688, and the 1932 Kinder Scout mass trespass.
Mass activity, political education and debate is the basis on which the labour movement in Britain will resolve its current crisis of political representation. This is what will determine whether the labour movement can reclaim the Labour Party or, failing that, whether the trade unions have to take the lead in re-establishing their mass party.
Whatever the outcome, the slogan coined by Lenin and the Communist International should continue to embody the spirit of May Day across the world: "Workers and oppressed peoples of all lands, unite!"
Robert Griffiths is general secretary of the Communist Party of Britain.
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