El Tanquetazo or El Tancazo (Spanish: "The tank putsch") was an attempted coup d'état that occurred in Chile on 29 June 1973.
Elements of an armored regiment of the Chilean Army led by Lieutenant Colonel Roberto Souper tried to overthrow the Popular Unity government of President Salvador Allende. Souper's regiment fired on buildings of the Chilean Government in central Santiago with tanks and small arms in which 22 people were killed. Loyalist soldiers led by Army commander-in-chief Carlos Prats successfully put down the coup within hours. Souper and most of the soldiers involved in the coup surrendered to Prats while some fled in exile to Ecuador.
The Tanquetazo was unsuccessful but is considered to have weakened Allende's Popular Unity government and contributed to the successful 1973 Chilean coup d'état three months later.
Background
By the beginning of June 1973, an important part of the high command of the Chilean Armed Forces had lost all respect for the Popular Unity government of President Salvador Allende, which had been in office since November 1970. During the so-called Tacnazo of 1969, high-ranking officers learned that by exerting pressure as a group, they could achieve wide-ranging changes within the military. In 1969 they had achieved high command changes and an increase in the Armed Forces' budget. In June 1973, some began plotting against the Allende government.
A week before the coup attempt, the conspiracy was discovered at the Santiago Army garrison. The garrison commander, General Mario Sepúlveda Squella, informed his immediate superiors at the Army General Staff, and also told José Tohá, the Minister of Defense. The government immediately arrested nine people involved in the conspiracy, and Minister Tohá decided to go public with this information on the afternoon of 28 June.
Putsch
Early in the morning of the following day, Lieutenant Colonel Roberto Souper, who had just learned that he would be relieved of his command for his part in the conspiracy, led a column of sixteen armored vehicles, including six M41 tanks, M3 half-tracks, plus 80 soldiers from the 2nd Armored Regiment in Santiago. The rebel column rapidly traveled to downtown Santiago from its base in Santa Rosa Avenue and encircled the presidential palace, La Moneda, and the building housing the Ministry of Defense, just across the Plaza de la Libertad. Two minutes before 9:00 AM, the tanks opened fire on these buildings.
At the Ministry, a tank made its way to the main entrance, climbed the steps into the building, and started firing on offices. Sergeant Rafael Veillena, of the Army's Second Division, was killed when he looked out a ninth-floor window. The firing of machine guns and tanks panicked workers in the area, who at that hour were making their way to their jobs downtown. A woman working at the State Bank near the Ministry was killed, as well as a couple who were caught in cross-fire. At least 16 people were wounded, four seriously. A group of foreign journalists covering the reforms carried out by Allende's government was caught in the middle of the insurrection. While filming the events outside La Moneda, Argentine cameraman Leonardo Henrichsen and his colleague Jan Sandquist were fired at by corporal Héctor Hernán Bustamante Gómez and several soldiers. Henrichsen was fatally shot by a soldier, who was never identified. Before collapsing in the arms of Sandquist, Henrichsen recorded the military foot patrol firing at him. The footage was recovered by Sandquist and shown on Argentine television on 24 July.
General Mario Sepúlveda Squella immediately called General Guillermo Pickering, commander of the military institutes, requesting loyal troops to suppress the rebellion. After securing these troops, he called Army Commander-in-chief General Carlos Prats with a plan to neutralize Souper's forces. General Prats approved it immediately, and a few minutes later General Sepúlveda Squella started to position his own troops.
Earlier that morning, Salvador Allende spoke to the people of Chile from the presidential residence at Tomas Moro in Santiago. In a 9:30 AM radio address, the president announced his unequivocal decision to defend the constitutional government against an attempted coup d'état. He called upon the workers of Santiago to occupy the factories "and be ready in case it is necessary to fight alongside the soldiers of Chile."