In 1984, Secretary of Defense Caspar W. Weinberger proposed six tests to determine whether US forces should be sent into combat: Is a vital national interest at stake? Will we commit sufficient resources to win? Will we sustain the commitment? Are the objectives clearly defined? Is there reasonable expectation that the public and Congress will support the operation? Have we exhausted our other options?

This became known as the "Weinberger Doctrine." It struck a harmonious chord with a generation that had learned hard lessons in halfhearted adventures from the Bay of Pigs to Vietnam to the Desert One fiasco in Iran. Thus it was that the Persian Gulf War of 1991--in marked contrast to the uncertain gradualism that characterized the Vietnam War--met all of the tests of the Weinberger Doctrine. For a change, military force was employed the right way. It worked, spectacularly.

From the first, though, the Weinberger Doctrine was an uncomfortable fit with the Clinton Administration, which came to office imbued with the idea that the instrument of military power could be and should be applied with fewer restrictions. President Clinton's first Secretary of Defense, Les Aspin, said that under the Weinberger rules, the armed forces would be employed "only very, very rarely" and that "people may not be willing to pay $250 billion or even $200 billion a year for a military that is not very useful."

That looser approach led to disaster in Somalia, where humanitarian relief turned into armed peacekeeping of a vague and tentative sort and eighteen US soldiers were killed trying to capture a warlord who was riding around on US aircraft two months later.

In a formal departure from the Weinberger Doctrine, Secretary of Defense William J. Perry said last year in his annual report to Congress that there are three basic instances in which the nation may use the armed forces. They can be employed not only for humanitarian missions and to protect vital interests--as in the Persian Gulf War--but also when "important but not vital interests are threatened," as in Haiti and Bosnia-Hercegovina.

A still greater divergence of policy was declared in a March 6 speech by National Security Advisor Anthony Lake, who presented the Administration's comprehensive position on the use of force. (Mr. Lake is a primary architect of the current national security strategy of "Engagement" abroad and "Enlargement" of democracy around the world.) He laid out "seven circumstances, which taken in some combination or even alone, may call for the use of force or military forces."

• To defend against direct attacks on the United States, its citizens, and its allies.
• To counter aggression.
• To defend our key economic interests.
• To preserve, promote, and defend democracy.
• To prevent the spread of weapons of mass destruction, terrorism, international crime, and drug trafficking.
• "To maintain our reliability, because when our partnerships are strong and confidence in our leadership is high, it is easier to get others to work with us."
• For humanitarian purposes, to combat famines, natural disasters, and gross abuse of human rights.

In the broader context of his speech, Mr. Lake said many of the right things, such as that "our tools of first resort remain diplomacy and the power of our example" and that the armed forces must be given "a clear mission with achievable military goals." Nevertheless, the threshold for commitment of US military force is lower than it used to be. Furthermore, our intentions are not always firmly resolved before we act.

Initial military operations in the Balkans were hampered by dangerously restrictive rules of engagement. In a 1994 encounter, an American AC-130 gunship circled above a Serbian tank that had shot at some French peacekeepers. The gunship could not fire until authorization came from UN officials in Zagreb who had gone to a Chinese restaurant without their cellular telephones. By the time permission was given, the Serbs had demonstrated their contempt and gone away.

In February 1996, looking back on restrictions that applied to air operations, Gen. Ronald R. Fogleman, USAF Chief of Staff, said that, "For many of us airmen, it was very reminiscent of what we had seen in Vietnam." Earlier, the New York Times had quoted American officials as saying the only logic for air strikes near Sarajevo in May 1995 had been to "drop a few bombs and see what happens" and that "there was no strategy behind any of this."

On August 30, 1995, NATO finally quit fooling around and launched Operation Deliberate Force. Airpower was authorized to strike the full range of Bosnian Serb military targets. Force was applied with focus and determination rather than with hedging and hesitation. Two weeks later, armed resistance ended, and the Dayton peace agreement was not far behind.

The Weinberger Doctrine specified when military force should be used. What the Lake Doctrine does, mainly, is categorize situations in which military force might be useful. Mr. Lake's list doesn't exclude much. It goes way beyond the defense of essential US interests. It can be interpreted to justify the use of force for almost anything. It sounds altogether too much like open-ended military commitment for purposes that are of limited importance to the nation. And that, of course, was what went wrong in Vietnam.