Oct. 1 marked the 30th anniversary of the signing in Washington of the Mutual Defense Treaty between the United States and the Republic of Korea, then only two months removed from a three-year war.
Most people in both countries have grounds to feel that the treaty has served its main purpose: Peace has, for this last generation, stood - uneasily, perhaps , on occasion, but far less queasily than we see it in several areas today.
Nor is there much evidence that peace will soon be broken. Northeast Asia is one of the world's historically most dangerous areas, nested amid great powers. US pledges of action against any renewal of aggression in the peninsula has been the cornerstone of this peace. Nor has Seoul shown any sign of military aggression on its own.
The costs, seen and unseen, have been high. The seen costs of our military aid to South Korea and of our own sending and stationing of troops - currently some 40,000, formerly much more - may have run to upwards of $20 billion or more , depending on how such costs are reckoned. Yet we have not always gotten so much for such expense as we have in South Korea.
The unseen wages are another matter.
The treaty has brought a deep, ineluctable militarization of our relations with Korea. Our aid, our presence, concentrated for 30 years on the military, have contributed to South Korean military dominance over all other forms of Korean institutional and political life, a condition wholly unnatural to one of the world's oldest antimilitary Confucian polities.
Crowning our efforts, a four-star American general - oddly termed ''United Nations commander,'' though with no other international forces and not answerable in any way to the UN - sits on the right shoulder of South Korean politics by virtue of his tactical command over some 90 percent of Korea's largest institution, the 600,000-strong armed forces.
We do not seek such position, perhaps. We try to draw the political fangs of the position. Yet no commander of a dominant army in a third-world country can be nonpolitical, however hard he might try. We fly in South Korea's political cockpit.
The consequnces of all this came home to us when a US general released Korean troops in his command to quell students and citizens struggling for democracy in Kwangju in May 1980, killing what some believe to have been 2,000. These iron measures consolidated the undemocratic reimposition of army control, political suppression, and censorship.
It also consolidated the opposition perception that the US ranges itself more against than for democracy in Korea. This perception has contributed to a rise in anti-American sentiment and the arson or bombing at three American cultural centers in Korea - Kwangju (December 1980), Pusan (March 18, 1982), and Taegu (Sept. 22, 1983). A Korean was killed in each of the Pusan and Taegu incidents.
If we seek to avoid in Korea the role of General Jaruzelski in Poland, we should, perhaps, more clearly read the Mene Tekels of our 30-year defense treaty.
Nor is it easy to keep the 30-year treaty from gnawing at our own political structure. Our military support and aid - the only such our government now gives - depends on estimates of North Korean strength obtained from constant overflights, satellites, and electronic surveillance. All this is completely beyond public, probably beyond civilian, control.
Only in theory do civilians and our elected representatives really control our policies. For the information on which this control must effectively rest lies far beyond their ken: literally toward the stars. Slowly, the form of government and controls James Madison and his fellows tried to bequeath us washes soundlessly away: ''A popular government without popular information or the means of acquiring it, is but the prologue to a farce or tragedy; or, perhaps, both.''
Our Defense Treaty is now a strapping warrior of 30 years. We salute him and even wish him more stout years. Would that he and all other militaries were nonpolitical.
Politics, alas, remains all, and military alliances remain to haunt us even when made without political intent. So is it, finally, with our Korean treaty. And who shall know whether the political effects will outbalance the military ones.