The Balkan Crisis: Military brains enter the fray: Christopher Bellamy in Split examines Serbian strategy that is creating order out of chaos

AT FIRST sight the Bosnian civil war may look chaotic, but there is a coherent strategy behind the seemingly mindless shelling, 'ethnic cleansing' and the besieging of small mountain towns.

Over the past month, for the first time, the Bosnian Serb army has begun to manipulate its forces in accordance with a plan that military professionals call the 'operational level of war' - the level between tactics and strategy. Some well-trained staff officers, schooled in the higher conduct of war, appear to be at work, though with relatively small forces.

It is doubtful whether the ceasefire initialled by the Bosnian Serbs and due for consideration by the Serbian parliament later this week will stop the war. In fact there are two wars. The big war involves the Serbs against the Muslims and Croats, whose commanders are united to some degree against the Serbian forces. However, the war within the war is the conflict between the Muslims and Croats at local level, and that is likely to continue.

Even if the bigger war ends, there has been a significant development in the last month. The Serbs have begun to co-ordinate the movement of whole formations against the main Bosnian formation, the mark of a trained general staff and an indication that they at least have overcome the whims of unpredictable local command to and impose a coherent concept on their conduct of the war.

The Bosnian Serb command has overcome the problems posed by small factions, each fighting its own local war, and has marshalled and distributed forces to deal a decisive blow. That blow is not being dealt at Sarajevo or Srebrenica - these are side- shows, distractions from which Bosnian Serb forces are being withdrawn. The decisive blow is to be struck in the Posavina corridor, linking Serbian positions in eastern Bosnia and the Serbian heartland with Serb-controlled areas in western Bosnia. Reports that Brcko has fallen to the Serbs suggest that the Serbian plan is having results.

The Bosnian Serb army comprises six corps - not 'corps' in the Nato sense, but formations of between 5,000 and 20,000 troops. Nor are they mechanised or infantry formations as a British general would understand them but heavily weighted towards mortars and artillery.

The picture changes from west to east. From the west as far as Travnik there is little determined fighting. Then comes the Maglaj Finger and an interesting contrast with the rest of Bosnia. Here, most of the Bosnian Serb fighters live in the area. They are farmers, and Maglaj is their local market town. There is no evidence that fighting here fits into any general staff's 'concept of operations'.

But to the east lies the critical Posavina corridor. Here a plan to defeat the Bosnian II corps based in Tuzla may be in operation.

The origins of the Serbian strategy lie in successful Muslim attacks on Serbia itself. The Serbian attack on Srebrenica in eastern Bosnia had three aims: to eliminate a threat to Serbian territory; to reopen the lines of communication across the Drina river blocked by the Muslim enclave of the same name, and to remove the Muslim inhabitants so the situation would not arise again. Whether those people were left dead or alive was immaterial. Unlike the Muslims and Croats, the Serbs do not seem to have appreciated the influence of media coverage on public opinion.

The Serbs have surrounded the pocket and partially solved their problem. But the Bosnian II corps remains a player. It has to try to reopen a corridor to Srebrenica, and to recapture the Posavina corridor. It would also like to capture Doboj - a Serbian stronghold perilously pinched between hostile thrusts. Doboj has been bombarded, but being Serbian, has not attracted the attention of Western television crews. Finally, II corps also has to defend Tuzla - a key Muslim city, crammed with refugees, with a crucial airfield. But II corps' main mission is offensive - the closure of the Posavina corridor.

The Serbian plan is workmanlike. First, destroy II corps' ability to resupply Srebrenica using helicopters - shell Tuzla airfield. Also, ensure there is no attack down the road from Kladanj to relieve Srebrenica. At the same time take pressure off the Posavina corridor by attacking II corps all round. The Serbian Drina corps and the Bijeljina corps are the main forces, probably reinforced by troops from the Sarajevo corps to the south- east and the Banja Luka corps to the west - four corps against one. Reports that the Serbs have captured Brcko on the river Sava suggest the Serbs are in sight of securing the corridor.

The corridor borders Croatia - indeed it falls into two parts: the Slavonian Posavina, in Slavonia, east Croatia; and the Bosnian Posavina, the 20-mile wide strip south of the river. The Croatian army is reported to have put its own troops in to the area. This indicates some interesting co-operation between Muslims and Croats at the higher level, notwithstanding the 'intercommunal' violence at the lower.

As the military theorist Basil Lidell Hart observed, a military operation differs from a surgical one because the patient is not tied down. Croatian and Muslim forces were applying pressure on Doboj. So the Serbs removed forces from Sarajevo and Srebrenica and launched an attack westwards behind the Bosnian forces attacking the Posavina corridor. This would cut them off from their base at Tuzla and effectively halt the attack on the critical corridor.

In military terms the attacks on Gorazde, Srebrenica and Sarajevo are of secondary importance, and the Serbs may be willing to give way on those issues to prosecute the 'real war' - the destruction of II corps.

The application of tried principles of war is not limited to the Serbs. The Bosnian Croat command - the HVO, based in Prozor - also has clear objectives: to secure the Croatian part of Bosnia, which they call Herzeg-Bosnia. They need to secure Jablanica, which lies astride the only metalled road into the area. They also want to link main towns like Kiseljak and Vitez.