WHAT SHOULD be happening in South Korea, in the wake of President Park Chung Hee's assassination, is this: the generals should be holding the ring while plans move ahead to let the civilians climb back into it and work out the country's future in a passably democratic way. But what has just actually happened is something very different -- and very ominous: the generals are preempting the civilians and climbing directly into the ring themselves.

In a midnight raid the other night, one clique of generals shot up another clique of generals. The attackers then took over the key position of martial law commander and forced three of their number into the key ministries in the interim cabinet. One does not have to be up on the internal politics of these various officers' groups to understand that a dark shadow has been cast over the whole prospect of a return to civilian rule.

The military in all too many places, of course, has shown itself adept at making up excuses for grabbing power. But South Koreans should understand they are in a special situation. They have just finished a long period, the Park period, in which the fact of military rule was a source of tension and trouble, especially in their relations with the United States.Is that what the generals want to ensure again?

Few people here probably underestimate the difficulties that face South Korea in removing the crude personal and institutional imprint of President Park and in turning toward a political system more consistent with the social and economic sophistication that South Korea has attained in recent years. But few also can probably look with any enthusiasm at the spectacle of a long-suffered ally conducting its affairs in the manner of an old-fashioned gang war. If the generals cannot agree among themselves to climb out of the political ring, they will be inviting a reaction from and a relationship with Washington quite different from that they presumably have in mind.