THE AMERICAN military's part in drug raids in Bolivia has to be understood as an act of mutual desperation. Bolivia's part is easy to understand. Pitifully poor, it stands to be overwhelmed by a cocaine trade whose revenues, greater than the national budget, give criminals the means to control the economy, corrupt institutions and buy national elections. In the United States, drugs are a health problem and then a social and law-enforcement problem. In Boliva, which lacks the institutions and resources Americans take for granted, drugs assault the very integrity of the state. That is what led its democratically elected president to take the political risk of inviting an American military intervention.

The United States has its own desperation, bred of a seemingly chronic inability to rein in a deadly scourge. The drug-bust statistics of the Reagan administration break records, but use and abuse of drugs break records too. Frustrated by the difficulty of cutting off the real engine of the drug trade -- the lure of the phenomenally rich American drug market -- the administration has turned up efforts to suppress this evil at the source. It has gone beyond the programs of earlier administrations to help willing producer nations eradicate drugs, plant substitute crops, beef up local law enforcement and improve their intelligence collection, and has been exploring ways to put American military forces directly into the battle.

For several years Air Force helicopters have been on drug patrol in the Bahamas, and Army units carried local forces to a raid in Colombia last February. A potentially momentous surge in activism came, however, in a secret presidential directive of April 8 stating, it is reported, the national security rationale for broad use of American military power to help foreign governments combat the international drug menace. The rationale is that the drug trade can destabilize political and judicial institutions. Bolivia is Exhibit A. American soldiers are there now ferrying a Bolivian strike force to the cocaine zones.

The initial congressional reaction to the American role seems mostly positive. But the new policy was devised in secret, and there has yet been little official elaboration or public discussion of it, so some important questions remain to be answered. There has been a general reluctance, not least in the military, to assign the military to a mission customarily treated as law enforcement. The terms on which American military forces might be committed, and American military men exposed to danger, are always vital questions. Careful, focused military-support operations could help, but people need to work first of all on the slow, hard, painful tasks of wringing drugs out of American society.