The M-19 guerrilla group, officially known as the Movimiento 19 de Abril, was a Colombian insurgent organization founded in 1970. It emerged in response to allegations of electoral fraud during the presidential elections. The group was known for its urban guerrilla tactics and aimed to promote social justice and political change in Colombia. M-19 gained notoriety for several high-profile actions, including the Palace of Justice siege in 1985, which resulted in significant casualties. The group eventually demobilized in 1990 and transitioned into a political party, contributing to the peace process in Colombia and the country's evolving political landscape.