President Chun Doo Hwan has turned to a trusted military academy classmate to broker a deal with South Korea's revitalized opposition movement and give new direction to the ruling party.

The emergence of retired four-star general Roh Tae Woo, 52, as Chun's top political operative has fueled speculation that he could become president in 1988 if Chun stands by a promise to step down that year.

As commander of an Army division based north of Seoul, Roh brought his troops into the capital in 1979 to back Chun, then also a general, in maneuvering following the assassination of President Park Chung Hee.

Lean and ruggedly handsome, Roh has since enjoyed a variety of senior posts in Chun's government. For the past two years, he has supervised preparations for the 1988 Seoul Olympic Games, the success of which is a great national objective here.

Late last month, Chun appointed Roh chairman of the ruling Democratic Justice Party. It was part of a general housecleaning in Chun's party and Cabinet brought on by major setbacks in National Assembly elections Feb. 12.

Roh's first task will be to work out an accommodation with the new Korea Democratic Party. Formed in January, it swept the cities with a campaign based on opposition to Chun's "military dictatorship."

Roh "has come out in front to get all the arrows and agonies from every direction," said a member of the ruling party. That role will allow Chun to stand back and appear to be above the fray.

In a meeting with foreign journalists last week, Roh said he felt the election had demonstrated that people want change. He said he was willing to open a dialogue with Chun's opponents.

"Opposition parties shouldn't be regarded as enemies," he said. But Roh suggested that face-to-face talks with Kim Dae Jung and Kim Young Sam, the new party's de facto leaders, would have to wait until both adopted "a new perspective" on South Korean politics.

Steps taken to date indicate Chun is opting for conciliation rather than retrenchment in response to the election. He has freed Kim Dae Jung from house arrest, restored the political rights of Kim Young Sam and 12 other politicians and loosened controls on the press.

Last Thursday, he made another gesture when a senior ruling party official asked a criminal court judge to show leniency toward 20 students facing charges for occupying the party's headquarters last fall.

Roh has been depicted publicly as a voice for moderation. Last week, a government statement on the lifting of political restrictions cited Roh's role in getting Chun to approve of the step.

Chun and Roh graduated from South Korea's military academy in 1955. Later, they attended a special warfare training course at Fort Bragg, N.C. In the late 1960s, they were together again, commanding Korean units in South Vietnam.

Both were young and obscure generals in 1979 when Park was shot by his intelligence chief. Backed by Roh and several other young generals, Chun seized full power in 1980.

The following year, after resigning from the military, Chun was elected to a seven-year term as president that expires in 1988.

Chun has been criticized, at times by his own supporters, as a distant and unresponsive leader whose staff can be afraid to give him bad news.

Roh, in contrast, is more personable and is said to have a better grasp of issues. He also lacks the "country boy" aura that has hobbled Chun's efforts to appear presidential.

There is no suggestion that Roh and Chun are near a falling-out. But the contrasts between the two are constantly commented upon here.

Speculation about Roh's political future has come about mainly because Chun's tendency to rule as a one-man show has resulted in no one being groomed to replace him.