Marcin Kasprzak was born on November 2, 1860, in Schmiedsruh (today Smardzewo), in the Province of Posen, then part of Prussia. He was the son of a laborer and grew up in a working-class environment that exposed him to the struggles of industrial workers during a period of intense economic and social change in partitioned Poland.

In 1885, Kasprzak moved to Berlin, where he became politically active by joining the Social Democratic Party of Germany (SAP), the precursor to the modern SPD. Inspired by Marxist ideals and the growing socialist movement, he soon returned to Poland and joined the revolutionary First Proletariat Party. His political activities quickly drew the attention of authorities, and in the same year he was arrested. Two years later, in 1887, he managed to escape imprisonment and fled abroad, first to Switzerland and then to Warsaw, where he secretly re-entered the country.

By 1888, the First Proletariat had collapsed, but Kasprzak helped to organize and establish the Second Proletariat, also known as the Small Proletariat. The group sought to revive the socialist revolutionary cause in Poland. Some historical accounts suggest that in 1889, Kasprzak also assisted in smuggling Rosa Luxemburg out of Poland, allowing her to continue her education and activism in Switzerland.

In the early 1890s, Kasprzak’s activism forced him into exile once again. In 1891, he relocated to London, a hub for political exiles from across Europe. However, in 1893, while attempting to cross into Russian-controlled Poland, he was arrested and imprisoned. After his release in 1896, he joined the Polish Socialist Party in Prussia, continuing his underground work among Polish workers.

Kasprzak’s revolutionary activity escalated when he returned to Russian-controlled Poland in 1904. By this time, he was a member of the Social Democracy of the Kingdom of Poland and Lithuania (SDKPiL), a party co-founded by Rosa Luxemburg and Leo Jogiches, which advocated Marxist revolution rather than Polish independence.

On April 27, 1904, Russian police discovered and raided an underground printing press in Warsaw. Kasprzak and his comrades resisted with armed force. In the ensuing gun battle, four policemen were killed and several others wounded. The event shocked the authorities, confirming the militant and violent tactics of Poland’s revolutionary underground.

Kasprzak was captured, tried, and convicted for his role in the deadly confrontation. He was sentenced to death and executed by firing squad on December 8, 1905, inside the Warsaw Citadel, a fortress notorious for housing political prisoners of the Russian Empire.