Each year on May 1, people across the globe take to the streets to commemorate International Workers' Day, or May Day.

In dozens of countries, May Day is an official holiday, and for labour rights campaigners it is particularly important.

The day commemorates past labour struggles against a host of workers' rights violations, including lengthy workdays and weeks, poor conditions and child labour.

Why is International Workers' Day on May 1?

In the late-19th century, socialists, communists and trade unionists chose May 1 to become International Workers' Day.

The date was symbolic, commemorating the Haymarket affair, which took place in Chicago, in the United States, in 1886.

For years, the US working class - often forced to work up to 16 hours a day in unsafe conditions - had been fighting for an eight-hour workday.

Then, in October 1884, the Federation of Organized Trades and Labour Unions of the United States and Canada decided that May 1, 1886, would mark the first day that an eight-hour workday would go into effect.

When that day arrived, between 300,000 and 500,000 US workers went on strike in cities and towns across the country, according to various historians' estimates.

Chicago, which was the nucleus of the struggle, saw an estimated 40,000 people protest and strike.

Until May 3, the strike was well-coordinated and largely nonviolent.



But as the end of the workday approached, striking workers in Chicago attempted to confront strikebreakers at the McCormick Harvesting Machine Company. Large police contingents were protecting the strikebreakers, and officers opened fire on the striking workers, killing at least two.

As the police attempted to disperse the protesters on May 4 in Chicago's Haymarket Square, a bomb was thrown at them, killing seven officers and at least four civilians.

Police subsequently rounded up and arrested eight anarchists, all of whom were convicted of conspiracy. A court sentenced seven to death and one to 15 years imprisonment. Four were hanged, one committed suicide rather than face the gallows and two had their sentences commuted to life in prison.

Those who died are regarded by many on the left, including both socialists and anarchists, as the "Haymarket Martyrs".

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In 1889, the Second International, the international organisation for workers and socialists, declared that May 1 would from then on be International Workers' Day. The Haymarket affair galvanised the broader labour movement.

In the US, however, the eight-hour workday wasn't recognised until it was turned into law in 1916, after years of strikes, protests and actions in favour of it.

What is the holiday's history after 1916?

After the eight-hour day was initiated in the US in 1916, it was endorsed by the Communist International, an international coalition of socialist and communist parties, and by communist and socialist parties in various countries.

In that same year, as World War I continued, partial strikes and clashes with police in the US and several European countries were fuelled by massive anti-war sentiment as much as they were driven by the struggle for labour rights.

In 1917, as the US declared its involvement in the war, socialists and other leftists demonstrated against the bloodshed.

Marxist leaders across the globe - among them Rosa Luxemburg and Vladimir Ilyich Ulyanov, who is most widely known as Lenin - considered the war to be an example of capitalist, imperialist countries pitting members of an international working class against one another. They argued that workers should unite and wage a revolutionary war against the ruling classes in their own countries.

Four days after the revolution that toppled Tsarist rule in Russia, the eight-hour workday was introduced by official decree.

What have been some of the most memorable International Workers' Day protests?

International Workers' Day is marked with celebrations, protests, strikes and commemorations around the world.

While the size and intensity of commemorations have ebbed and flowed over the years, several International Workers' Day commemorations stand out.

In the US in 1971, as the war in Vietnam continued under the presidency of Richard Nixon, protests in Washington, spanned several days and included civil disobedience against the war.

Nixon sent in an estimated 10,000 troops and mass arrests were made, prompting accusations of civil rights violations. Police and security forces arrested more than 12,000 people, although most were eventually released without charges.

More recently, in 2006, a series of US-wide immigration reform marches continued on May 1, when organisers called for a strike they named a "day without immigrants". Protests had already drawn the participation of between 350,000 and 500,000 people in cities across the US.

In 2016, large May Day protests and marches were held in countries across the world. In the Turkish city of Istanbul, protesters clashed with police while trying to reach the city's iconic Taksim Square. At least one protester was killed and dozens arrested.

READ MORE: May Day - US workers' struggle, then and now

In Moscow, tens of thousands of Russians marched in a pro-Kremlin rally to commemorate the holiday, while left-wing groups held separate events in several Russian cities.

In Taipei, Taiwan's capital, labour unions took to the streets with a march to call on the government to reduce working hours and increase wages.

Thousands of people in the German cities of Berlin and Hamburg participated in public demonstrations. Protests against the far-right Alternative for Germany (also known as AfD) party were held in several German cities.

What should you expect in 2019?

Following France's nationwide "yellow vest" protests that began in November last year, about 7,400 policemen are expected to be deployed in Paris.

Observers say most of those joining the ranks of the "yellow vest" movement are workers on lower middle incomes who say they barely scrape by and get scant public services in exchange for some of the highest tax bills in Europe.

Although planned protests to commemorate May Day take place every year in France, clashes between protesters and riot police may take place as they have become regular occurrences following the latest wave of demonstrations.

Interior Minister Christophe Castaner has warned that up to 2,000 "radical activists" may try to "sow violence and disorder" and may join up with "radicalised" protesters from the "yellow vest" movement.

Castaner said there was also a risk that "radical elements" could try to infiltrate trade union marches in other cities, even though the unions themselves were committed to avoiding any violence.

In neighbouring Germany, the German Trade Union Confederation has called for traditonal May Day demonstrations in favour of a European-wide minimum wage.

Police have said a total of 5,500 officers will be deployed in Berlin including 2,000 in Friedrichshain, and have called on demonstrators to remain peaceful.

Thousands of trade union members will also march through Asia, including the Philippines, Malaysia, Indonesia, Taiwan, Cambodia and Myanmar.

In Sri Lanka, major political parties called off traditional May Day rallies due to security concerns following the Easter bombings that killed 253 people and were claimed by members linked to ISIL.