Marxist–Leninists in the context of Classical Marxism

In Marxism, ultra-leftism encompasses a broad spectrum of revolutionary Marxist currents that are anti-Leninist in perspective. Ultra-leftism distinguishes itself from other left-wing currents through its rejection of electoralism, trade unionism, and national liberation. The term is sometimes used as a synonym of Italian left communism. "Ultra-left" is also commonly used as a pejorative by Marxist–Leninists and Trotskyists to refer to extreme or uncompromising Marxist sects.

The Official Irish Republican Army or Official IRA (OIRA; Irish: Óglaigh na hÉireann) was an Irish republican paramilitary group whose goal was to remove Northern Ireland from the United Kingdom and create a "workers' republic" encompassing all of Ireland. It emerged in December 1969, shortly after the beginning of the Troubles, when the Irish Republican Army (IRA) split into two factions. The other was the Provisional IRA. Each continued to call itself simply "the IRA" and rejected the other's legitimacy.

Unlike the "Provisionals", the "Officials" did not think that Ireland could be unified until the Protestant majority and Catholic minority of Northern Ireland were at peace. The Officials were Marxist–Leninists and worked to form a united front with other Irish communist groups, named the Irish National Liberation Front (NLF). The Officials were called the NLF by the Provisionals and "stickies" by nationalists in Belfast (apparently in reference to members who would glue Easter lilies to their uniforms), and they were sometimes nicknamed the "Red IRA" by others.

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.