International Workers' Day in the context of Anti-revisionism

K-Groups (German: Kommunistische Gruppen, lit. 'Communist Groups') is a term referring to various small, Maoist organizations and political parties that sprang up in West Germany at the end of the 1960s, following the collapse of the Socialist German Students' Union (SDS), and general collapse of the West German student movement. K-Groups played a particularly important role within the New Left in West Germany during the first half of the 1970s. The term "K-Group" was used primarily by competing left-wing groups and in the media. It served as a collective term for the numerous, often fiercely divided groups and alluded to their shared self-image as communist cadre organizations.

Various organizations referred to as K-Groups included the Communist Party of Germany/Marxists–Leninists (KPD/ML), the Communist Party of Germany (Organizational Structure) (KPD-AO), the Communist League (KB), the Communist League of West Germany (KBW), the Communist Workers Union of Germany (KABD), and the Bavarian-based Workers League for the Reconstruction of the KPD [de] (AB).

The Socialist International, commonly known as the Second International, was a political international of socialist and labour parties formed in Paris on 14 July 1889. At a time of growing industrial working-class movements and the expansion of suffrage, it brought together autonomous national parties into a loose international federation. It continued the work of the First International (1864–1876), from which it inherited both the legacy of Karl Marx and the conflict with anarchists. The organization was dominated by the powerful Social Democratic Party of Germany (SPD), whose organizational and theoretical leadership heavily influenced the other member parties.

The International established the annual celebration of International Workers' Day on 1 May and popularised the demand for an eight-hour day. Its early congresses were preoccupied with expelling anarchists and defining its mission as one based on parliamentary political action. After 1900, the International was increasingly confronted with the internal divisions of the socialist movement, particularly the rise of revisionism in Germany and the debate over socialist participation in "bourgeois" governments, sparked by the Millerand affair in France. The 1904 Amsterdam Congress, which saw a major debate between French socialist Jean Jaurès and German leader August Bebel, condemned revisionism and ministerialism, marking the highest point in the influence of the International.

In politics, a red flag is predominantly a symbol of left-wing ideologies, including socialism, communism, anarchism, and the labour movement. The originally empty or plain red flag has been associated with left-wing politics since the French Revolution (1789–1799). The red flag and red as a political colour are the oldest symbols of communism and socialism.

Socialists adopted the symbol during the Revolutions of 1848. It was first used as the flag of a new authority by the Lyon Commune and Paris Commune in the aftermath of the Franco-Prussian War (1870–1871). The flag of the Soviet Union, introduced during the Russian Revolution, as well as the flags of many subsequent communist states, were explicitly inspired by the plain red flag. Many socialist and socialist-adjacent political parties, including those of democratic socialists and social democrats, have adapted and adopted a red flag as their symbol. The plain red flag was an official symbol of the Labour Party in the United Kingdom until the late 1980s. It was the inspiration for the socialist songs "The Red Flag" and "Bandiera Rossa".

The Bloody May Day (Turkish: Kanlı 1 Mayıs, lit. 'Bloody 1 May' or 1 Mayıs Katliamı, '1 May Massacre') was an attack on leftist demonstrators on 1 May 1977 (International Workers' Day) in Taksim Square, Istanbul, Turkey. Casualty figures vary between 31 and 36 people killed with 126 to 220 injured. Over 500 demonstrators were later detained by the security forces, and 98 were indicted. None of the perpetrators were caught, although suspicion soon fell on the Counter-Guerrilla and associated right-wing groups. The massacre was part of the wave of political violence in Turkey in the late 1970s.

May Day is a European festival of ancient origins marking the beginning of summer, usually celebrated on May 1, around halfway between the Northern Hemisphere's spring equinox and midsummer solstice. Festivities may also be held the night before, known as May Eve. Traditions include gathering green branches and wildflowers ("bringing in the May"), which are used to decorate buildings and made into wreaths; crowning a May Queen, sometimes with a male companion decked in greenery; setting up a Maypole, May Tree, or May Bush, around which people dance and sing; as well as parades and processions involving these. Bonfires are also a major part of the festival in some regions. Regional varieties and related traditions include Walpurgis Night in central and northern Europe, the Gaelic festival Beltane, the Welsh festival Calan Mai, and May devotions to the Blessed Virgin Mary. It has also been associated with the ancient Roman festival Floralia.

International Workers' Day observed on 1 May is also called "May Day", but the two have different histories.

Socialism in the United States has encompassed various types of tendencies, including utopian socialists, anarchists, democratic socialists, social democrats, Marxist–Leninists, and Trotskyists. These movements trace their origins back to utopian communities that took root in the early 19th century, such as the Shakers, the activist visionary Josiah Warren, and intentional communities inspired by Charles Fourier. In the 1860s, immigration from Europe of radical labor activists, particularly of German, Jewish, and Scandinavian backgrounds, led to the establishment of the International Workingmen's Association in 1864 and the Socialist Labor Party of America in 1877.

During the 1870s, socialists of various tendencies actively participated in early American labor organizations and workers' demands to improve working conditions, as well as to officially recognize and practically implement the basic labor rights. These grievances culminated in the 1886 Haymarket massacre in Chicago, which resulted in the death of eleven people. One of the consequences of this tragic event was the establishment of International Workers' Day, which was proclaimed as a fundamental labor holiday. Apart from that, workers' organizations and socialist parties worldwide made the establishment of an eight-hour workday their primary objective.