Little-known Gen. Chun Doo Hwan has emerged from the South Korean military hierarchy as a key figure and the subject of intense speculation because of his role in the military action taken here on the night of Dec. 12.

Chun is the leader of a group of four or five younger generals who that night directed a military uprising that led to two shootouts in Seoul and the arrest of the Army chief of staff. Those developments set off a new convulsion in South Korean politics.

Who he is and what he wants are still the main unanswered questions here. Diplomats worry about what motivates him. His name has not appeared in the press that his command censors, but when something important happens, the first question certain to be asked is: "Did Chun do that?"

Usually knowledgeable sources are divided on his role. They agree he was the key military figure on the night of the uprising. He gave the command to pick up his boss, Gen. Chung Sung Hwa, and issued an unauthorized order that moved troops friendly to him to secure Seoul.

They are divided on how much power he has wielded since. Some sources say he is still in command. Others think he is part of a collective leadership that has reshuffled the military hierarchy and is only one power among several.

A distinguishing trait of Chun and the younger military officers is a strong sense of Korean nationalism, according to sources familiar with their thinking. They were in awe of the late president Park Chung Hee and admired his frequent admonitions that Koreans developed native institutions and "self-reliance." Mixed with that, it is said, is a streak of anti-Americanism that has not been evident among older officers who fought with American troops during the Korean War.

Chun himself is described as a bright and aggressive infantry officer who has come as far as anyone in his class of 1955 at the Korean Military Academy.

Personal descriptions of him are similar. He is said to be a man of considerable presence -- "a take-charge kind of man," in one source's description. He is also said to have a streak of abrasiveness that did not endear him to older generals, such as former defense minister Ro Jae Hyun and Chung.

He was described by one acquaintance as feeling that Ro, Chung and other older generals exercised military favoritism and blocked promotions for those of his generation.

"The younger generals were angry with Chung and Ro and they in turn were angry at Chun," said one Asian diplomat who is familiar with this country's military. "They thought he was too arrogant and aggressive and did not show respect for the older generation."

Many in Seoul regard this generation conflict as the key to the military upheaval.

Chun was a leader of the group of officers who graduated from the first four-year class at the Korean Military Academy. They are said to think of themselves as the country's first truly professional soldiers and to look patronizingly on their seniors who got a few months of professional instruction before making their careers in the war of 1950-53.

Chun, one of the most successful in his class, was bright enough to win a brief term as a military aide in Park's presidential office.

At the time of Park's assassination on Oct. 26, Chun was, and still is, defense security commander, which places him in charge of military intelligence and investigations. It is mostly a military command, but it also has investigated civilian dissidents over the years, and ordered many of them beaten and tortured in a post known colloquially as the "Bingo Hotel" in Seoul. Several street demonstrators reportedly were beaten severely there last month.

After the assassination, he was placed in charge of the martial-law command's joint investigation unit, which investigated the plot to kill Park.There, according to his spokesman, he and associates developed doubts about the role played on the fatal night by their boss, Chung, who had by then become martial-law commander as well as Army chief of staff. Chun's office has produced no evidence publicly to show that Chung was involved in the plot.

He has told outsiders that he considered the integrity of the military to be at stake since Chung was known to have been near the scene at the time of Park's death. Failing to question Chung, he has told them, would compromise the military for years.

Chung is being held for alleged conspiracy in the assassination of Park because he had received a large sum of money from the convicted assassin, the South Korean Defense Ministry said today.

A 25-page report said Chung had received the money from Kim Jae Kyu -- who was sentenced to death last week -- in early October. It also said Chung had shown an "opportunistic attitude" on the night of the slaying.

The report disclosed for the first time that three persons -- a major, a corporal and a sergeant -- were killed and four others seriously wounded during a shootout following Chung's arrest at his home Dec. 12.