In the United States, this debate--which frequently pits the military versus the "civilian" arms of the government, including the State Department and the White House--has resurfaced with each major conflict and intervention since the second World War.

As Alexander George has written, in the wake of the ambiguous results of the Korean War of the early 1950s, one school of thought began to argue that the United States should "never again" fight such an inconclusive war of half-measures. Either the United States should commit to using "all or nothing" to win or it should avoid armed intervention abroad altogether. By contrast, other foreign policy strategists contended that incertain cases in which important US interests were at stake, it would be necessary to call on military force to wage "limited wars" to defend them.

The Vietnam War crystallized this strategic debate, and imprinted indelible lessons upon a generation of future military leaders. For many, the failure in Vietnam began early on with the the gradual escalation of involvement, the constrained application of force, and the meddling of politicians in war's operational details. "The war in Vietnam was not lost in the field, nor was it lost on the front pages of the New York Times or on the college campuses," Vietnam author, Major H.R. McMaster has written. "It was lost in Washington, D.C., even before Americans assumed sole responsibility for the fighting in 1965 and before they realized the country was at war."

Through its so-called "hollow force years" of the 1970s and beyond, the military faced new missions and further humiliations. During the Carter administration, the failed hostage rescue attempt in Iran in 1980 undermined the military's prestige. Moreover, despite the vast military build-up of the Reagan years, the 1983 bombing of the US Marine barracks in Lebanon, at a loss of 241 lives, encouraged another stock taking.

The "lessons" of the Vietnam War and Beirut loomed large in November of 1984, when Reagans Secretary of Defense Caspar Weinberger gave an influential speech embracing many of the military's concerns. The "Weinberger doctrine" contained six points sharply limiting the use of combat forces:

• Either the United States' or its close allies' vital national interests had to be at risk;
• The war had to be fought "wholeheartedly, with the clear intention of winning";
• We should employ decisive force in the pursuit of clearly defined political and military objectives;
• We must constantly reassess whether the use of force is necessary and appropriate;
• There must be a "reasonable assurance" of Congressional and public support;
• Force should be used only as a last resort.

Admittedly, the Reagan administration's application of the Weinberger doctrine was never as orthodox as the defense secretary's six criteria might suggest. The repeated confrontations with Libya throughout the 1980s are but one example of the administration's willingness to calibrate military force to fit limited strategic goals.

It was the Persian Gulf War in 1990-1991 that seemed to validate many of Weinberger's central points: the United States had a clear and vital interest in the region's oil, military action was largely supported by the public, Congress and key allies, and evicting the Iraqi's from Kuwait was the kind of well-defined, achievable objective the military could embrace. Most importantly, the American victory suggested that the use of decisive amounts of firepower and troops would avoid the incremental escalation that contributed to the debacle in Vietnam.

Nevertheless, late in his administration George Bush began grappling with the challenges inherent in the United States position as the sole superpower in a post-cold war world. Speaking at West Point in January 1993, Bush offered a more flexible set of guidelines while reiterating the need to maintain a clear and achievable mission.

The most notable articulation of policy on use of force came not from Bush, however, but from the Chairman of the Joint Chiefs of Staff, Colin Powell. A Vietnam War veteran, former military assistant to Secretary Weinberger and Gulf War hero, Powell stressed the "lessons learned" in Vietnam and reiterated the insistence on using force only when objectives are clearly defined and results reasonably achievable.

And while Powell accepted the post-cold war need for the military to undertake peacekeeping and humanitarian missions, he posed a series of questions, or tests, that should be asked in situations which required the use of "violent" force:

Is the political objective we seek to achieve important, clearly defined and understood? Have all other nonviolent policy means failed? Will military force achieve the objective? At what cost? Have the gains and risks been analyzed? How might the situation that we seek to alter, once it is altered by force, develop further and what might be the consequences?

In 1993, with the arrival of President Clinton, doctrine governing the use of military force faced several key tests. None would prove more lasting than Somalia, where in October 1993, the United States' involvement took a turn toward disaster. From its origins as a limited humanitarian effort during the Bush administration, the Somalia intervention had evolved into a broader peace-keeping mission ‚ a mission that was shattered when 18 lightly-armed troops were killed in a firefight with guerillas loyal to Mogadishu warlords. The strong military and public reactions to the televised images of a helicopter pilots body being dragged through the streets led to a rapid American pull-out.

The Somalia experience engulfed deliberations within the Clinton Administration over how to deal with the deteriorating civil war in Bosnia. As a presidential candidate, Clinton had sharply criticized President Bush's failure to stop the bloodshed in the Balkans. However, once in office, Clinton's campaign rhetoric ran head-long into the cautionary questioning of General Powell, who had publicly voiced concerns about intervention in Bosnia.

While Clinton did mobilize some 20,000 troops in 1994, in an effort to help build democracy in Haiti, administration policy on Bosnia muddled along for more than two years. Finally in mid-1995, the bombing of a Sarajevo marketplace touched off what was, at the time, NATO's largest military action--"Operation Deliberate Force." Diplomats claimed victory when the two-week calibrated bombing campaign, assisted by an aggressive Croat-Muslim offensive on the ground, pushed the Bosnian Serbs to the negotiating table and, ultimately, to the Dayton Peace Accords.

Based in part on the Bosnian experience, Clinton's national security adviser Anthony Lake gave a speech in early 1996, outlining the beginnings of a new force doctrine. Once again, the ultimate goal was to avoid "Vietnam-like quagmires" and muddled interventions such as Lebanon and Somalia. Nevertheless, Lake's speech suggested that the post-cold war world required a broader and more flexible policy regarding the use of force than was outlined in either the Weinberger or Powell doctrines.

To better define what constituted an area of US national interest, Lake listed seven broad sets of circumstances for using force ranging from a direct attack on the United States or its allies to curtailing drug trafficking and ending gross abuses of human rights. When it came to actually using force, Lake came up with three key principles:

• Credible threats of force can be as effective as force itself;
• The "selective but substantial use of force is sometimes more appropriate than its massive use";
• Carefully defined exit strategies should accompany every foreign intervention.

Lake placed particular emphasis on the last point, and argued that "tightly tailored military missions and sharp withdrawal deadlines must be the norm." Calling his policy "tough love" and warning against "dangerous hubris," Lake argued that the US could not "build other nations. But where our own interests are engaged, we can help nations build themselves and give them the time to make a start of it." In the case of Bosnia, Lake saw the US troops staying to enforce a one-year "window of opportunity" that would expire at the end of 1996.

On the ground in Bosnia, the administration's policy would be sorely tested as the senior military and diplomatic officials -- Admiral Leighton "Snuffy" Smith and Ambassador Richard Holbrooke -- battled over the implementation of the hard-won Dayton Accords. For "maximalists" like Holbrooke, Dayton's lesson was that force had been essential to stopping the war, and would be needed to support efforts to build a new peace. By contrast, Smith argued that the military had been given a more limited mandate and resources, and he warned against the kind of "mission-creep" that he believed had characterized previous intervention disasters, like Somalia, Beirut and Vietnam.

Both opinions reflected the reality that while shooting in Bosnia had subsided, a stable peace that would allow for the exit of American troops had not been achieved. Indeed, in late 1997 President Clinton finally announced that, after missing several deadlines, no further dates for troop withdrawal would be set.

As violence escalated in Kosovo in early 1999, following the collapse of the Rambouillet peace talks, the Clinton Administration and its NATO allies turned again to the peace-building formula that had won agreement at Dayton: a calibrated and escalating air campaign designed to force a peace agreement. However, Serb recalcitrance in Kosovo, including the continued mass expulsion of ethnic Albanians, has proven a tough test of the administration's new "bombs for peace" strategy-- bringing to the fore the central and recurring questions about when, where and how military force should be used.