As is customary in most Spanish-speaking countries, he was given both his parents' last names, Somoza being his father's last name and DeBayle being his mother's last name. DeBayle is of French origin.
Anastasio Somoza DeBayle, nicknamed "Tachito" (Spanish: Little Tacho) by his father, was the third child of Anastasio Somoza García and Salvadora DeBayle. At the age of seven, he was enrolled at the Instituto Pedagógico La Salle, run by the Christian Brothers. One of his classmates was Pedro Joaquín Chamorro Cardenal, who would grow up to become one of the most prominent opponents of the Somoza dynasty. From the age of ten, Tachito was educated in the United States. He and older brother Luis Somoza Debayle, both attended St. Leo College Prep (Florida) and La Salle Military Academy (Long Island). He passed the examination for West Point, entered the United States Military Academy on July 3, 1943, and graduated on June 6, 1946. Two years after his return from West Point, he fathered a daughter, Patricia, who was later sent to a series of schools abroad. Also after his return, he was appointed chief of staff of the National Guard, (Nicaragua's national army), by his father, who had previously given many important posts to family members and close personal friends. As commander of the Guard, Somoza was head of the nation's armed forces, effectively the second most powerful man in Nicaragua. On 10 December 1950, he and Hope Portocarrero, an American citizen and his first cousin, were married at the Cathedral in Managua by Archbishop Jose Antonio Lezcano. Over 4,000 guests attended the ceremony. The reception was given by Somoza's father, President Anastasio Somoza García, in the luxurious and modern Palacio de Comunicaciones. The couple had five children:Anastasio Somoza Portocarrero
Julio Somoza Portocarrero
Carolina Somoza Portocarrero, married to James Minskoff Sterling, son of New York real estate developer Henry H. Minskoff
Carla Somoza Portocarrero
Roberto Somoza Portocarrero
Following his father's assassination on 21 September 1956, Somoza's elder brother, Luis, took over the presidency. Anastasio had a large hand in the government during this time, and saw to it that the presidency was held by politicians loyal to his family from 1963 to 1967.
On 1 May 1967, shortly before the death of his brother, Anastasio Somoza was sworn into office following his election on 5 February. While Luis had ruled more gently than his father had, Anastasio would not tolerate opposition of any sort, and his regime soon resembled his father's in all significant respects.
With regard to educating the workforce, Somoza famously replied, “I don’t want an educated population; I want oxen.”
His term in office was due to end in May 1972, due to a law which disallowed immediate re-election. However, prior to that, Somoza worked out an agreement allowing him to stand for re-election in 1974; he would be replaced as president by a three-man junta consisting of two Liberals and one Conservative while he retained control of the National Guard. Somoza and his triumvirate drew up a new constitution that was ratified by the triumvirate and the cabinet on April 3, 1971. He then stepped down as president on May 1, 1972. However, as head of the National Guard, he remained the de facto ruler of the country.
On 23 December 1972, an earthquake struck the nation's capital, Managua, killing about 5,000 people and virtually destroying the city. Martial law was declared, making Somoza the country's ruler in name as well as in fact once again. He then took over effective control as head of the National Emergency Committee. He reportedly embezzled many of the funds sent from across the world to help rebuild Managua. Some parts of Managua have still never been rebuilt or restored, including the National Cathedral. Somoza also allegedly exported freshly imported emergency blood plasma abroad, at the time of the earthquake, when most medical supplies in Nicaragua were desperately in short supply.
Somoza was re-elected president in the 1974 election. By this time, the Catholic Church had begun to speak against his government. (Indeed, one of his fiercest critics was Ernesto Cardenal, a leftist Nicaraguan priest who preached liberation theology and would become the Sandinista government's Minister of Culture.) By the late 1970s, human rights groups were condemning the record of the Somoza government, while support for the Sandinistas was growing inside and outside the country.
In July 1977, Somoza had a heart attack, and went to the US to recuperate.
In 1975 Somoza Debayle launched a campaign to crush the Sandinistas; individuals suspected of supporting the Front were targeted. The Front, named after Augusto César Sandino (a Nicaraguan rebel leader in the 1920s), began its guerrilla war against the Somozas in 1963 and was funded by the Soviet Union and Cuba under Fidel Castro. Support for the Sandinistas ballooned after the earthquake, especially when U.S President Jimmy Carter withdrew American support for the regime for human rights reasons.
At this point, the opposition to the Somozas included not only Sandinistas, but other prominent figures such as Pedro Chamorro (assassinated on January 10, 1978). Israel was the last supplier of weapons to the Somoza regime, because during the Israeli War of Independence in 1948, Somoza's father provided substantial financial support for Israel. Carter forced the Israeli government to call back a ship carrying weapons vital to the survival of the Somoza regime.
Because of his status, most of his family members were forced to flee into Honduras, Guatemala, and the United States. It is uncertain where the remaining Somozas live given the fact that they changed their names to protect their own lives.
On July 17, 1979, Somoza resigned the presidency and fled to Miami in a converted Curtiss C-46. He took with him the caskets of his father and brother and, it is claimed, much of Nicaragua's national treasure leaving the country with, it is claimed, a $1.6 billion foreign debt, the highest in Central America. After Somoza had fled, the Sandinistas found, it is claimed, less than $2 million in the national treasury.
Somoza was denied entry to the U.S. by President Carter. He later took refuge in Paraguay, then under the dictatorship of Alfredo Stroessner. He bought a ranch and a gated house at Avenida de España no. 433 in Asunción. Somoza's regime lasted only another day, when his successor peacefully handed Managua to the Sandinistas.
Somoza was assassinated near his exile home on September 17, 1980. He was 54 years old. Somoza Debayle was ambushed by a seven-person Sandinista commando team (four men and three women). This was known as "Operation Reptile".
The Sandinista team had two Soviet-made machine guns, two AK-47 assault rifles, two automatic pistols, and an RPG-7 rocket launcher with four anti-tank grenades and two rockets. The leader was Argentinian Marxist revolutionary Enrique Gorriarán Merlo (code named "Ramon"), an ex-Ejército Revolucionario del Pueblo member. One of the team members said: "We cannot tolerate the existence of millionaire playboys while thousands of Latin Americans are dying of hunger. We are perfectly willing to give up our lives for this cause."
For over six months the Sandinista assassins researched and planned their assault. The team meticulously studied Somoza's movements with a team member who was staked out at a newspaper kiosk near the estate. They waited in ambush for Somoza in Avenida España. Somoza was often driven about the city in a presumed unarmored Mercedes-Benz S-Class sedan. Team member Oswaldo, disguised as a paper boy, watched Somoza exit the estate and signaled when he was leaving at 10:10 A.M.
Once in position, Hugo Irurzún (Capitán Santiago) readied the RPG-7. He tried to fire an anti-tank rocket at the car, but the RPG-7 misfired. Ramon then gunned down the chauffeur while Irurzún quickly reloaded the RPG with a new rocket. The second rocket made a direct hit on the sedan. Accounts mentioned that the Mercedes' engine kept on running even after the rocket explosion. Previously the commando team had considered the possibility that Somoza's vehicle might indeed be equipped with armor panels in front. This would most likely deflect the rocket projectile upwards if hit from a frontal stance. The Sandinista team decided to engage with a lateral attack which would rule out any projectile deflection. Somoza was killed instantly and charred with the other two passengers in the car, his financial advisor, Colombian citizen Jou Baittiner  and his new driver César Gallardo. Later media reports in Paraguay stated that Somoza's body was so unrecognizable that forensics had to identify him through his feet.
Of the seven assassins, six escaped. Irurzún was later captured because of his blond beard and was executed.
Somoza was buried in Miami, at Woodlawn Park Cemetery and Mausoleum. A few months before Somoza's death, his memoirs, Nicaragua Betrayed, were published. In them he blamed the Carter Administration for his downfall. His son, Anastasio Somoza Portocarrero, went into exile in Guatemala.
Former National Intelligence Officer for Latin America and Cuba Brian Latell argues in his book, After Fidel, that the plan to assassinate Somoza was devised in Havana with direct input from Fidel Castro. According to him, the Sandinistas had won power in July 1979 with the assistance of massive, covert Cuban military aid. Along with his brother Raúl Castro, the two masterminded a complex multinational covert action to provide the Sandinistas with huge quantities of modern armaments. Latell claims Cuban intelligence and paramilitary advisors poured into Nicaragua along with the equipment. Latell argues the evidence indicated that the assassination operation was similar to other assassination operations Cuban intelligence had been involved in, and that Somoza was a long-time nemesis of Castro after he provided critical support to the U.S. in preparing for the Bay of Pigs Invasion of Cuba in April 1961. Jorge Masetti, a former Argentine guerrilla working with Cuban intelligence services, describes the Somoza assassination and Cuba's direct role in the planning in his autobiographical book, In the Pirate's Den.
Somoza's funeral became an occasion for wealthy Nicaraguan and Cuban exiles in South Florida to gather and protest the left-wing governments of Nicaragua under the Sandinista National Liberation Front and Cuba under Castro. However, other accounts note that this group in Miami was also relieved at Somoza's death because the newly founded Contra army, which consisted of many ex-members of Somoza's National Guard, would have had to give the impression of having no relation to the old Somoza regime, for purposes of public relations and world opinion.
In 1979, the Brazilian newspaper Gazeta Mercantil estimated that the Somoza family's fortune amounted to between $2 billion and $4 billion with its head, Anastasio Somoza Debayle, owning $1 billion.
Somoza was the subject of the 1983 film Last Plane Out, in which he was portrayed by actor Lloyd Battista. The film chronicles journalist Jack Cox's journey to Nicaragua, when Somoza was battling insurgents. The same year, he was depicted in Under Fire, set during the 1979 Nicaraguan Revolution, this time portrayed by actor René Enriquez. In Warren Beatty's Rules Don't Apply, Somoza is portrayed by Julio Oscar Mechoso.
His assassination was reported in the "famous" tabloid headline "Somoza slain by bazooka".