SINCE THE MOMENT the United States absently accepted Japan's surrender there in 1945, it has tried 1) to make South Korea a firm rampart of the American-led anti-communist security system and 2) to build democracy. But only the first of these goals has been achieved. Koreans and Americans who have argued that South Korea would be more secure if it were a democracy have been beaten back by those asserting that democracy is irrelevant if not inimical to security in the Korean context. The trouble is that North Korea's hostility has justified a size and centrality for South Korea's army that gives the generals a continuing temptation and rationale for seizing power.

The generals now tightening their grip seem to have made a cynical but precise calculation. They could see that Washington's growing anxiety over a Soviet threat had reduced chances that Jimmy Carter or a successor would take real steps to reverse their grab for power. They could guess that Peking's general situation and Moscow's preoccupation with Afghanistan made it unlikely that North Korea would take military advantage of fresh political turmoil.

The administration, however, has scarcely gone through the motions of dismay. Nothing could better demonstrate its business-as-usual approach than its gauchely timed, on-schedule dispatch of an Export-Import Bank mission to Seoul to conduct . . . business as usual. "We would prefer that it be in a democratic mode but it is not up to the United States to tell South Korea what its politics should be," the bank's president explained.

So now the United States, having failed to build democracy in South Korea, is openly offering to help build dictatorship. It is a sorry spectacle. For notwithstanding Seoul's difficulties in staying on the straight and narrow path to democracy, it is a country with a genuine democratic impulse. Not just its intellectual elite but a broadly based spectrum of Korean citizens have demonstrated this by word and deed for three decades. Not least among them are the entreprenuers and technocrats responsible for the Korean "economic miracle."

There is an anti-communist consensus in South Korea, but there is a constituency for democracy, too. By suppressing it, the generals assure it will burst out anew; their very effort to anticipate the challenge will weaken the country from within.