He was the founder and main leader of the Manuel Rodriguez Patriotic Front, in which he was well known as "Comandante José Miguel", "Rodrigo" or "Benjamín".

[1] In 1976, his family moved to Cuba where he pursued a career in medicine, but a few months later, he decided to leave college to take up a military career, joining the school Camilo Cienfuegos which is dependent on Cuba's Revolutionary Armed Forces (FAR).

Over there, he lived with nearly one hundred Chilean military personnel under the support of the government of Fidel Castro.

From that school, Pellegrin graduated in late 1978 with the rank of lieutenant.

In early 1979, he decided to travel to Nicaragua to support the struggle of the Sandinista National Liberation Front (FSLN), which sought to overthrow President Anastasio Somoza Debayle.