Complex sentence: The "Dirty War" was the term dubbed to the atrocities committed under the military dictatorship of Argentina during 1976 to 1983, which began by the coup d'état that overthrew President Isabel Peron and the accession of a military junta led by General Jorge Rafael Videla.
Split into simpler sentences: The "Dirty War" was a series of the atrocities committed under the military dictatorship of Argentina during 1976 to 1983. The dictatorship began with a coup d'état against President Isabel Peron followed by the accession of a military junta led by General Jorge Rafael Videla.