When Otis Cary interrogated Japanese prisoners during World War II, he softened them with gifts of magazines, cigarettes and chocolates. He broke through their reserve with humor. And he spoke to them in flawless Japanese — shocking from a blond-haired American.

Cary spoke like a native because he was one — the son and grandson of New England missionaries in Japan. With missionary-like ardor, he proselytized for the Allied cause, persuading many of the prisoners to cooperate in efforts to end the war and help rebuild Japan as a democracy.

"Prolonged contact with Americans in the prison camps clearly had an impact on many prisoners, and for none more than those influenced by Otis Cary," wrote Ulrich Straus, a former diplomat whose study of Japanese prisoners of war, "The Anguish of Surrender," was published in 2003.

Cary, 84, who died of pneumonia April 14 in Oakland, California, played a unique role in U.S.-Japan relations during and after World War II.

He was one of the 1,100 Japanese linguists trained by the Navy to serve as interrogators, translators and interpreters after the 1941 attack on Pearl Harbor. For more than four decades after the war, he bridged cultures as a professor of American studies at Doshisha University in Kyoto.

Cary was, in many respects, more Japanese than American.

"When Americans asked him where he came from, he said it pained him to say he was from Massachusetts," said Donald Keene, a Columbia University expert on Japanese literature and a longtime friend, who served with Cary during the war.

"To tell a fellow officer 'I came from Japan' was to start a quarrel" in the tense period after Pearl Harbor, Keene explained. But Cary, he noted, "saw Japan as his real home."

Cary's deep understanding of the Japanese enabled him to help the POWs overcome their shame at having been captured and their fears of returning home in disgrace. He encouraged them to see themselves as patriots, who had given their all to their country and who now had a duty to support its reconstruction.

He counted among his "converts" POWs who went on to become leaders in the new Japan, including the publisher of a major newspaper and a prominent physician. He also drummed ideas of democracy into members of the imperial family, whom he met on several occasions after Japan's surrender in August 1945.

In 1947, while Japan was still under the Allied occupation, he joined the faculty of Doshisha University as a representative of Amherst College. In 1991, he helped launch Doshisha's graduate school of American studies, the first of its kind in Asia.

For 32 years, he was director of Amherst House, a dormitory where he encouraged Japanese students to dispense with customs that he considered obstacles to modernization.

One of his targets was honorific speech, which mandates different degrees of politeness depending on a person's social rank. To put students on an equal footing, Cary just gave them nicknames.

"It was a very innovative idea," said Shigeki Hijino, a former Newsweek correspondent who lived at Amherst House in the early 1960s. In Hijino's view, Cary's greatest achievement was broadening the minds of the hundreds of students who passed through Amherst House over the years. "He produced so many students who have gone beyond Japan," said Hijino, now a freelance journalist in Stockholm.

"Otis Cary played a key role — I believe an under-recognized one — in helping to ease U.S.-Japan relations, both socially and at the academic level," said Pedro Loureiro, curator of the Pacific Basin Institute at Pomona College, which promotes Asian studies. "Otis was a very humble person who accomplished a lot."

Cary is survived by his wife of 61 years, Dr. Alice S. Cary; three daughters: Beth Cary of Oakland, Ann Cary of Osaka, Japan, and Ellen Cary Bearn of Bethlehem, Pa.; one son, Frank of Tokyo; and five grandchildren.

He was born Oct. 20, 1921, on Hokkaido, the northernmost island of Japan. He moved to the United States after elementary school and attended high school at Deerfield Academy in Massachusetts. From there, he went on to Amherst College, which had a long history of ties with Japan through an exchange program with Doshisha University.

When America entered World War II, Cary enlisted in the Navy and breezed through its crash course in the Japanese language at UC Berkeley and the University of Colorado. Assigned to a POW camp at Pearl Harbor in early 1943, he became executive officer of the interrogation section. His first interrogation subject gave up information vital to the Allied offensive in the Aleutians after the prisoner learned that Cary was from his hometown of Otaru.

As the first officer to greet the POWs when they arrived at the Hawaii camp, Cary devised a rather elaborate ritual to set them at ease.

As recounted by Straus, Cary lined up the prisoners and called their rank, beginning with the lowest rank first. Privates first class were asked to take one step forward, the next highest rank two steps forward, and so on. Cary generally ran out of prisoners by the time he reached lieutenant or captain but continued the exercise until he reached the highest ranks.

"What, no generals or admirals?" he would ask, feigning shock when no one stepped forward. "With that," wrote Straus, who interviewed former POWs and their interrogators, "Cary won his audience. The men burst out in prolonged laughter at the absurdity of thinking that persons of such august rank would ever become prisoners."

Cary spoke to the POWs in colloquial Japanese, even though he was capable of navigating the language's many levels of politeness. He did this, Straus explained, to break down the Japanese military's stiflingly strict rank system and allow natural leaders to emerge.

Cary refused to rough up prisoners and treated them as his equal. He always had larger objectives in mind.

"Otis believed in treating prisoners very well," Frank B. Gibney, another former Navy interrogator who went on to become a prominent journalist and author of books about Japan, wrote a few years ago in an unpublished autobiography. (Gibney died April 9.)

"He saw the Japanese as a lay missionary sees them — good grist to be talked to and milled, made friends with, and, one hopes, ultimately brought to understand the virtues of American democracy, if not Christianity."

Cary organized a group of POWs to assist in writing propaganda and surrender leaflets. According to Straus, the group's most important contribution was its swift translation of the Potsdam Declaration, the July 1945 statement drafted by three Allied leaders — Harry S. Truman, Winston Churchill and Chiang Kai-Shek — that delineated the terms for Japan's surrender.

The document had been suppressed by the Japanese government, so Cary's POWs translated it for dissemination in leaflets dropped from B-29s all over the country. The leaflets dispelled widespread fears in Japan that the surrender terms would be excessively punitive and put pressure on the Japanese government to accept the declaration a few weeks later.

Cary's influence was so strong, Straus said, that his name "was the only one cited repeatedly" by many former POWs years later in written accounts of their wartime captivity. For many of the prisoners, Cary was the one who brought their families the news that they were alive.

Ingrained with the ancient samurai code that it was a disgrace to be taken prisoner, many of the Japanese POWs wanted to be thought dead. Their government felt the same way and sent death notices to their families. When Cary was assigned to duty with the Allied occupation, he carried many letters from POWs back to Japan, often delivering the missives after the families had held their funerals.

One of the letters went to the family of Isamu Nakano, a Japanese naval officer captured in Guam. After the war, Cary helped him get a job at Doshisha, where he served as caretaker of Amherst House for 25 years. He is now 93 and living in Kyoto.

"Otis changed my dad's life," said Nakano's son, Takaharu, an international business consultant in Kyoto. "He saw hope in following this man and believed his life would be changed. We have been very much blessed because of his help to my dad."

During the early months of the occupation, Cary became acquainted with Emperor Hirohito's youngest brother, Prince Takamatsu, and his wife, Princess Kikuko. He suggested to the prince that the emperor, who by tradition was considered a deity, begin to show a more human side by traveling among the people and releasing informal photographs of the imperial family engaged in aspects of daily life. Shortly thereafter, the emperor began to do that.

During one conversation with the prince, Cary referred to the emperor as the prince's "big brother," a deliberate attempt to compel the prince to view the emperor as a mortal.

According to an account Cary gave in his 1975 book "War-Wasted Asia: Letters 1945-46," the royal sibling found the concept startling. A short time later, however, he published an article in Japan with a surprising headline: "My Big Brother, the Emperor." Hirohito renounced his divinity a short time later.