The same Carter administration document that contemplates losing one-third of West Germany to a Soviet attack contends that removing U.S. troops from South Korea gives Washington "flexibility" to determine whether or not to intervene against Communist invasion from the north.

PRM (President Review Memorandum) 10, a top secret inter-agency study of U.S. force structures, also is gloomy about holding the South Korean capital of Seoul if North Koreans invaded today. Even with U.S. air and naval intervention in South Korea, the study suggests, Seoul could not be held.

All this contradicts President Carter's assurances that his decision to remove the 2nd U.S. infantry division does not undercut the U.S. commitment to South Korea. It also undermines current military doctrine based on the retention of Seoul as a necessity. Thus, South Koreans face the same problem as the West Germans: Shall they believe public pronouncements of U.S. leaders or private documents 1of their staff experts?

The administration's claim that PRM-10 merely discusses options is simply untrue. Just as PRM-10 states that present allied forces could not hold one-third of Germany, its disturbing comments on Korean are based on conditions before and after the U.S. troop pullout, not on any option.

"Once the U.S. land forces are out of Korea," says PRM-10, "the U.S. has transformed its presence in Asia from a land-based posture to an off-shore posture. This . . . provides the U.S. flexibility to determine at the time whether it should or should not get involved in a local war."

The document goes on to reveal an unpublicized reason for removing the 2nd division: to give Washington the choice of whether or not to intervene. With the troops gone, sayd PRM-10, "the risk of automatic involvement (which was a major factor in removing land force from Korea) is minimized. However, should the U.S. decide to internvene, military forces would be readily available."

Even with the 2nd division still on station and the U.S. supplying "initial air and naval support at D-Day," PRM-10 spins a grim scenario: "If the North Koreans were to achieve tactical surprise, it is possible that they could at least temporarily attain their most likely major objective - the capture of Seoul."

While predicting North Korea could not win "a sustained combat," it predicates this on major U.S. help. "With the U.S. contributions of land and carrier-based tactical air assets and material support, it would appear that the U.S. and ROK [Republic of Korea] would prevail against North Korea in the longer term, but with possible initial setbacks - including perhaps the fall of Seoul."

Without U.S. help, the situation is desperate, according to PRM-10: "The level of forces which could be brought to bear at the front on D-Day would generally favor North Korea over the ROK in all categories . . . The ROK has widely spread infantry forces with limited mobility and vulnerable stocks of war materiel."

The document implies a return to the old U.S. strategy of keeping allied troops away from the DMZ and instead falling back on Seoul. Now-retired Lt. Gen. James Hollingsworth changed that when he took command nearly four years ago, contending the North Koreans wanted to capture Seoul quickly and then start debilitating peace negotiations. So, allied strategy changed to a forward defense of Seoul.

Such a defense requires Korean confidence in U.S. readiness to supply indispensible air power. South Korea long has worried that its defense pact with Washington provides a less automatic U.S. response to invasion than does the NATO treaty. President Carter's July 25 letter sought to reassure President Park Chung Hee that the U.S. troop pullout does not mean "any change whatsoever in our commitment."

PRM-10 undercuts all of South Korea's expectations. While emphasizing that only U.S. air and naval intervention could stop an invasion, it now makes that intervention a matter of choice rather than automatic response.

After our column reported that PRM-10 assessment of a Soviet attack in Central Europe, a senior West German army officer secretly visited Washington to find the truth. Interviews with 30 people, the general said, left "not the shadow of a doubt in my mind" that the column was accurate despite White House denials. South Korea's generals may now begin in a similar process with hopes that the answer will be more reassuring that the findings of their German counterpart.