Is there a difference between "peace enforcement" - limited strikes on recalcitrant warring factions, such as those against the Bosnian Serbs in autumn 1995 - and limited war, as it was waged in the Gulf or the Falklands. If so, what is it?
There is, they said this week. And the key, they say, is impartiality. Their conclusions were announced at a three-day conference on international peace-keeping held in the Indian Army Room at Sandhurst and were given in a talk by Lieutenant-General Mike Jackson, the former commander of the British- led, south-western sector in Bosnia. He is now commander of Nato's Rapid Reaction Corps.
Traditionally, the British have not been good at "doctrine". But, starting with the publication in 1994 of the provisional British doctrine for "Wider Peacekeeping", they have found themselves in the forefront of the debate. The Indian Army Room was an oddly appropriate setting - all that imperial policing made the British experts in dealing with "complex emergencies", such as Bosnia, Rwanda and Somalia.
"Wider Peacekeeping" set out a model in which traditional peace-keeping - policing an agreement between two former warring sides - and "wider peacekeeping" - maintaining peace and assisting humanitarian aid in a volatile environment - were separated from more warlike military operations by the line of consent.
The warring parties broadly consented to the peace-keepers being there, and even if there were shoot-outs with unruly members of the warring factions, as in Bosnia, that did not violate the overall consent.
Crossing the consent line, what Gen Sir Michael Rose called the "Mogadishu line" after the US switch to more warlike operations in Somalia in October 1993, was akin to crossing the Rubicon.
Once a peace-keeping force shattered the consent which was the authority for its presence, there might be no way back. On the other side lay peace enforcement and war. Nobody had addressed the issue of whether there was a real difference between them.
In August 1995 the Western powers crossed the Rubicon in Bosnia with air and artillery strikes against the Serbs. It was recognised they had crossed over to "peace enforcement", but nobody was clear how that differed from limited war.
"The key doctrinal issue is whether and if so in what way peace enforcement differs from war", Gen Jackson said. Gen Jackson produced a diagram with two lines, one dividing peace-keeping from peace enforcement, as before, and one dividing peace enforcement from war. The latter was labelled "impartiality". If consent was the Mogadishu line, impartiality can perhaps be seen as the "line in the sand" that led to the 1991 Gulf War against Iraq.
"The idea was that peace enforcement and war were more or less the same thing. That once you crossed the Mogadishu line you were at war", he said. The reluctance to switch to more aggressive measures against the Bosnian Serbs sprang in part from a conviction that once you crossed the Mogadishu line you might find yourself at war. Had the existence of a second barrier been recognised, the UN and Nato might have crossed the Mogadishu line and hit the Serbs sooner.
Both peace-keeping and peace enforcement come under the heading of "peace support operations". These, Gen Jackson explained, "are designed to conclude conflict by conciliation among the competing parties, by helping to overcome the underlying causes of conflict rather than a superficial termination of the conflict by force. Thus, a more stable settlement, not military victory, is the ultimate measure of success and the use of military force will be constrained by the long-term requirements of peace building".
The main difference between peace enforcement and war was impartiality. In peace enforcement, it was directed against anyone who violated agreements. The key difference from war is there was no designated "enemy". Peace enforcement is defined as "coercive operations carried out to restore peace in a situation of chaos or between belligerent parties who may not all consent to intervention."
If there is little inclination by the parties to agree to peace-making, a readiness to fight and escalate might be appropriate. If such a doctrine had existed in 1992, it is possible the UN would have gone into Bosnia and Somalia on that basis and not as "peace-keepers".
"We went through a real Alice in Wonderland world where we had peace- keepers keeping a non-existent peace, safe areas that weren't safe", Gen Jackson said. With a second boundary established in the uncharted area beyond the consent line, that may not happen again.