At various times in his 91 years, Deno Geanakoplos played the part of a soldier, a concert musician and an absentminded — but brilliant — professor. But his son, John Geanakoplos ’75, said the Bradford Durfee professor emeritus of history was first and foremost a passionate, enthusiastic and loving father.

Geanakoplos, who died last Thursday of pneumonia, was born in 1916 in Minneapolis, Minn. He began teaching Byzantine and Renaissance history at Yale in 1967, after working at the University of Illinois and Brandeis University, and produced over 13 books and 100 journal articles over the course of his career. He was the recipient of the Gold Cross of the Order of King George I — a Greek decoration awarded to him for his cultural contributions — in 1966 and was named Archon “Teacher of the People” by the Patriarch of the Greek Orthodox Church in Constantinople in 1975. Geanakoplos also received Guggenheim and Fulbright grants.

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Geanakoplos’ two children, John Geanakoplos — an economics professor at Yale — and Constance Geanakoplos ’80, said their father remained committed to their family up to his last days.

“In the last couple of years, he hadn’t been doing very well, and near the end he could only say about three things,” John Geanakoplos said. “He’d say that he was cold, that the food was bad and that he loved us.”

Those who knew him remembered Geanakoplos’ intellectual verve. Deno and John Geanakoplos were one of only a handful of father-son pairs in the University’s history to be tenured professors at the same time. For one semester, they taught in adjacent classrooms in William L. Harkness Hall.

“At every point where I stopped in my lecture to gasp for breath, I would hear the clarion calls of my son,” Deno Geanakoplos told the Yale Weekly Bulletin and Calendar in 1986.

John Geanakoplos remembered his father as an “excitable lecturer” who became so distracted when his son visited him in class that he bungled his presentation on ‘The Six Reasons Why the Schism of 1064 Could Have Been Dated at Another Time.’

“He skipped from reason number three to reason number six, and he totally forgot about numbers four and five,” John Geanakoplos said.

John and Constance Geanakoplos said their father always took pride in his children’s achievements. In addition to his post at Yale, John Geanakoplos’ achievements include the United States Junior Open Chess Championship in 1970. Constance Geanakoplos is a concert pianist in New York City. Their father’s favorite topic of conversation was his children, to the point that it was “a little embarrassing,” John Geanakoplos said.

Wayne Meeks, professor emeritus of religious studies at Yale, described Geanakoplos as both a gifted and unconventional professor.

“Always looking slightly disheveled, he filled his pockets with notes scribbled on backs of old envelopes and departmental memos,” Meeks said in an e-mail. “How could Yale undergraduates relate to a teacher who rushed into class at the last minute, frantically pulling out yet more notes and launching into what always seemed the middle of a learned narrative he had begun somewhere else? But they did! He was a marvelous teacher.”

Geanakoplos’ former students remember his animated teaching style.

“He was probably a little impromptu, which was very refreshing,” Margaret Little ’77 said.

Richard Jackson GRD ’92, who studied with Geanakoplos in the late 1970s, said he recalls his former professor’s office in the Hall of Graduate Studies as filled with “teetering and tottering” stacks of papers and books. Geanakoplos was “famously absentminded,” Jackson said, but always managed to give memorably brilliant lectures — something Geanakoplos said he enjoyed.

“I get a wonderful kick out of giving a good lecture,” Geanakoplos said in a 1986 interview with the Yale Bulletin. “It’s like giving a good performance on the violin. It’s a wonderful means of communicating feelings and ideas.”

In addition to being an esteemed professor, Geanakoplos was also a gifted musician. He earned a degree from the Julliard School of Music in 1939 for playing the violin and went on to play as first violinist in the Minneapolis Symphony Orchestra from 1939 to 1942.

“There was something similar in the way that he approached music and academics,” Constance Geanakoplos said. “In that way, he was Dionysian as opposed to Apollonysian. He could totally lose himself in something.”

Constance Geanakoplos said she remembers finding a tattered copy of sheet music composed by Bach that used to belong to her father. In the margins of the music, next to a particularly effective harmonic sequence, Deno Geanakoplos had scrawled the phrase “Incredible piece!!!” to no one in particular.

“A concert violinist before he turned to scholarship, he had an artist’s approach to teaching, to scholarship, and to life,” Meeks said.

Geanakoplos served in the U.S. military from 1942 to 1945, rising through the ranks from private to captain. During this time, he learned the local languages of the countries where he was stationed. Geanakoplos also enrolled in classes at the University of Pisa, eventually writing his dissertation on medieval history in Italian in 1945.

Geanakoplos was fluent in nine languages: English, Italian, Latin, French, German, Russian and ancient, Byzantine and modern Greek. He loved to travel, and whenever he visited Greece or Italy, he would ask locals to guess what region of the country he came from — they usually speculated that he was Sicilian, his son said.

Geanakoplos’ parents were among the first Greeks to settle in Minneapolis and helped found the city’s Greek community, John Geanakoplos said. Geanakoplos was proud of his family’s heritage and maintained cultural involvement with the Greek Orthodox Church. In 1976, he represented the Greek-American community at the Ellis Island commemoration of the American bicentennial.

A lifelong enthusiast of etymology, Geanakoplos enjoyed explaining the roots of every English word, and took great pleasure whenever those roots were Greek.

Geanakoplos was married for 48 years to Effie Geanakoplos, a Yale professor of psychiatry who died in 2001. They met while they were both studying at Harvard. Geanakoplos knew right away that he wanted to marry her, but they waited five years for Deno Geanakoplos to finish his dissertation before they wed, John Geanakoplos said.

In addition to academia, languages and travel, Geanakoplos loved sports and athletics. He jogged two miles every day until he was 69 years old, when he suffered a heart attack, John Geanakoplos said.

“He was a fine tennis player, though I never had the chance to play with him,” said Giles Constable, a professor emeritus at the Princeton School of Historical Studies. “He was much too good for me.”

Geanakoplos also enjoyed playing football, golf, ping-pong and bowling with his family.

“He never quite caught on that you were supposed to let the kids win,” John Geneakoplos said. “That was never really his style.”

Geneakoplos was a voracious and fast reader, often devouring multiple books in a day, Constance Geanakoplos said. He spent much of his time writing letters to old friends throughout Europe.

Funeral services will be held today at 11 a.m. at St. Barbara’s Greek Orthodox Church on 480 Racebrook Road in Orange, Conn.