Lt. Colonel Roberto Federico Souper Onfray was a Chilean military officer who launched an unsuccessful coup d'etat against the regime of Salvador Allende, surrounding the presidential palace with a tank regiment.
This coup, known as the Tanquetazo, took place on June 29, 1973. Souper's failure is considered significant in that it provided the military with a valuable lesson as to what conditions were necessary for a coup to succeed. The American government is suspected of having sponsored Souper, but many potentially relevant documents remain classified.