The colors themselves were born in Italy by Italian Anarchists in 1877. They entered a small Italian town called Letino, sporting the Black and Red in one of many failed attempts to provoke rebellion.
However, it wasn't until the Spanish organization CNT (Confederacion Nacional del Trabajo) formed an alliance with the FAI (Federacion Anarquista Iberica) during the Spanish Civil War and used it as their flag that it was acknowledged and internationally known as a symbol, at this point represtenting syndicalism.
The colors of the flag are symbolical. The Black stands for the origional Anarcho-flag, which was simply just black. The Red stands for Communism.

The CNT-FAI were and still are syndicalists (unionists). The Spanish Civil War began in 1936 and ended in 1939. The Anarchist revolution is one of histories greatest performances of intolerance and hatred for violent oppression and poverty, and at the same time love for themselves, their families, and others who had to live under the ruthless dictatorship of General Primo de Rivera and his oppressive police; la Guardia Civil. One of the most beautiful displays of Anarchism was done by the CNT-FAI. When they took a life sized statue of Jesus, dragged it into the Spanish Court of Law, and tried him for crimes against the people. Jesus was found guilty and sentenced to death, courtesy of the Anarcho-Firing Squad.........
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