Sergio Arellano Stark, a Chilean army general who led the “Caravan of Death,” a helicopter-borne killing squad that helped establish Augusto Pinochet’s iron grip on power in the 1970s, died March 9 in the capital city of Santiago. He was 94.

The cause was complications from Alzheimer’s disease, his family said.

Gen. Arellano was described as a principal instigator of the bloody Sept. 11, 1973, coup that deposed Salvador Allende, Chile’s democratically elected Marxist president, and installed army general Pinochet as head of state.

Empowered by martial law, Gen. Arellano became a crucial enforcer of violent measures to ensure the junta’s survival. Effective dissent was all but wiped out through repression, and Pinochet ruled as president for 17 years, a tenure darkened by human rights violations and corruption.

“The Caravan of Death was the first and foremost death squad in the days after the coup,” said Peter Kornbluh, director of the Chile documentation project at the Washington-based National Security Archive.

Retired Chilean army Gen. Sergio Arellano in 1997. (SANTIAGO LLANQUIN/Associated Press)

“The intent,” he added, “was to eliminate the local civic and political leadership who had done nothing wrong other than participate in the democracy that Allende represented at the time, as well as to send a very forceful message to local military commanders that peaceful coexistence with the left in their communities would no longer be tolerated.”

Leading the brutal spree of torture and extrajudicial killings, Gen. Arellano hopscotched from town to town in Puma helicopters with his handpicked retinue, methodically hunting down perceived dissidents and checking off names from a list as they were eliminated. The group was alleged to have killed or “disappeared” at least 75 Chileans, reportedly ranging in age from 16 to 85.

During Pinochet’s reign, an estimated 3,000 Chileans were killed or went missing, and thousands more endured torture, with most violations occurring in 1973, according to a government report on the atrocities.

On his ominous helicopter flights, Gen. Arellano visited military commanders in distant provinces, mainly the mining region of the arid north, an Allende stronghold. His mission was to root out officers deemed too soft on leftist activists and other alleged subversives.

The caravan descended from the sky with troops in battle fatigues brandishing weapons as if in combat. Their aggressiveness surprised some provincial military commanders, who had been prepared to greet them with military marches and other festivities befitting dignitaries.

“Perhaps you don’t realize that we are at war!” Gen. Arellano snapped to one commanding officer, according to the late Chilean journalist Patricia Verdugo’s book about the Caravan of Death, loosely translated as “In the Claws of the Puma.”

Everyday enlisted soldiers were forced to participate in gruesome summary executions of prisoners who had been locked up on flimsy charges. Many civilians had surrendered voluntarily because they trusted local officials to protect them, Kornbluh said.

Throughout the northern region, in cities such as Calama, Antofagasta and Tocopilla, the death caravan orchestrated kidnappings, murders and mutilations. Bodies were sometimes tossed down mine shafts or left to decay in the parched Atacama Desert. The victims included lawyers, professors, journalists, doctors and labor leaders.

In 1978, two years after Gen. Arellano’s retirement, Pinochet decreed a sweeping amnesty law protecting the military from prosecution for human rights crimes committed in the first five years of his dictatorship.

In an effort to circumvent the amnesty law, the Chilean supreme court made an exception in 1999 for victims whose bodies remained missing and whose cases could be considered unresolved kidnappings.

That decision opened the door for investigations into Pinochet and retired military officers including Gen. Arellano, both of whom were placed under house arrest.

A major break in the caravan case, according to Kornbluh’s book “The Pinochet File,” was a public statement in 2001 by a retired military commander in the north at the time of the coup.

In an interview with a Chilean TV station, Gen. Joaquin Lagos Osorio said that Gen. Arellano had shown him paperwork in 1973 documenting his authority as Pinochet’s official delegate and his order to “review and accelerate” the judicial process.

Lagos also provided a vivid account of the death squad in action.

“They cut eyes out with daggers. They broke their jaws and legs,” Lagos said, adding that firing squads were used to inflict maximum pain instead of instant death. “They shot them to pieces, first the legs, then the sexual organs, then the heart, all with machine guns. . . . They were no longer human bodies. I wanted to at least put the bodies back together again, to leave them more decent, but you couldn’t.”

Gen. Arellano had long denied responsibility for the killings, saying local military garrisons disobeyed his instructions.

In 2008, the Chilean supreme court ruled that he should serve six years in prison, citing his role in the deaths of four people in the town of San Javier. The sentence was suspended because of his rapidly deteriorating mental health.

Sergio Víctor Arellano Stark was born in Santiago on June 10, 1921, and rose through the military ranks in the infantry. Following training at the Command and General Staff College at Fort Leavenworth, Kan., he was a military aide in the 1960s to President Eduardo Frei Montalva and served as a military attache in Spain.

After his army retirement, hastened by apparent conflicts with members of the regime, Gen. Arellano was involved in various business ventures. His wife, Raquel Iturriaga, predeceased him. They had two children. A complete list of survivors was not immediately available.

Pinochet died in 2006, at 91, still combating human rights charges and insisting his leadership had been a necessary bulwark against communism in the southern cone countries of South America. His defenders, overlooking the human toll, say that he salvaged the country’s battered economy and set Chile on a course of booming growth.