SEOUL » "If anyone could be a marine, I’d never have joined." That is the slogan of South Korea’s Marine Corps, and it speaks volumes about the force’s sense of its elite status; it is a particularly bold assertion in a country where most able-bodied men perform mandatory military service.

These days, however, that marine pride, and the discipline of the South Korean military in general, has come under uncomfortable scrutiny.

In June, some marines fired their rifles toward a civilian passenger plane approaching the Seoul airport, mistaking it for a North Korean aircraft in an episode that has raised questions about the marines’ training and preparedness. (Fortunately, they did not hit the plane.)

But a series of very different episodes that followed in quick succession this month have proved even more troubling for many South Koreans.

On July 4, a marine corporal who investigators said was bullied by others in his barracks went on a shooting rampage, killing four marines and wounding a fifth. On July 10, a marine private hanged himself. Bruises, possibly from an earlier beating, were found on his chest. Four days later, a marine master sergeant killed himself, also by hanging.

These episodes, and similar ones in the army, have amplified a problem faced by South Korea’s 650,000-member military, a force intended to deter aggression from North Korea, with which the South never concluded a formal peace after the 1950-’53 Korean War. Increasingly, the military’s ranks are filled with young men who have not experienced war and no longer consider their 21-month compulsory service a "sacred duty," as their fathers did, but rather an inconvenient interruption of their civilian lives and careers.

That shift in attitude not only has worried superiors who count on a motivated force, but also has led to a generational clash. Many younger soldiers and marines are now unwilling to accept harsh treatment long tolerated and even encouraged in South Korea as a way of toughening up men for battle, including beatings severe enough to puncture eardrums and cut deeply into thighs.

Even conservatives, like President Lee Myung-bak, have indicated they believe that times have changed and that the military needs to find a new way of maintaining discipline other than through physical assaults.

"Some young people, who grew up in freedom, seem psychologically unable to adjust to a different environment in the military," the president said, commenting on the deaths among the marines. "We have to drastically change the barracks culture."

The Defense Ministry has announced a crackdown on beatings and other abuses in the military. It also vowed to eradicate a practice that many consider a bedrock of military life here but that has also been blamed for widespread brutality: the "order and obey" system, according to which soldiers and marines with seniority are encouraged to devise harsh penalties for their subordinates, and even beat them, in order to punish failure and enforce obedience to the smallest of rules and traditions. In some barracks, privates must get a superior’s permission even to use the bathroom.

The system is especially strong in the marine corps, which accepts only volunteers and where members strongly adhere to a pecking order based on entry-class seniority — a new class arrives every two weeks. Many former marines remember with dread the 5-pound pickax handle wielded by more senior marines as their favored flogging tool.

To many veterans, the proposed changes threaten a cherished tradition and the South’s security, even as the North has continued provocations, including an attack in November on a South Korean island guarded by marines.

"You obey marines from an earlier class as if they were gods," said Kim Jong-ryeol, a 51-year-old former marine who runs a truck weighing station in Seoul. "This is what drives marines through a hail of bullets in wartime. What they’re trying to do now is to kill the marines’ soul, to turn them into sissies. The only one who’ll be pleased by this is Kim Jong Il," the North Korean leader.

One of the veteran’s sons, Kim Soong-nyong, 26, who completed his service in the marines in 2008, agreed. "Everyone who volunteers for the marines knows that he’ll have to put up with beatings and other stuff that makes marines what they are: tough," he said. "The military is not a summer camp for kids."

But the calls for change have grown more urgent since the wave of military deaths, and after a series of human rights reports lifted the veil on many harsh military practices.

In March, the National Human Rights Commission criticized "customary and widespread beatings and cruelties" among marines and a "culture where subordinates consider enduring them a ‘marine corps tradition."’

The effort to revamp military life has broader implications. "Garrison culture" has long been cited as a force that both drives and ails South Korean society.

Since nearly all men are military veterans, the code of ethics they practice in their years in the services tends to bleed over into civilian life, and corporate offices. The benefits are clear: South Korea’s powerful companies and institutions carry out projects quickly and efficiently, many say, because of the ethos of not questioning orders and showing respect for superiors.

Workers who fall short are often chided by colleagues who ask, "Weren’t you in the military?"

But analysts have also blamed that same culture for stifling individual initiative, instilling tolerance of physical violence in school and at home and encouraging people in business or the government to turn a blind eye to corruption.

"From their military service, South Korean men learn to tolerate irrationalities," said Lim Tae-hoon, director of the Center for Military Human Rights in Korea.