The struggle for the Balkans: How the opposing forces line up in the former Yugoslavia equired

Christopher Bellamy explains the strengths and strategies of the armies massing in western Bosnia and Croatia

Croatia's armed forces have spent the years since their defeats by Serb rebels and invaders in 1991 building their strength with arms and training from abroad - mainly from the former Warsaw Pact. In the spring they executed a small but efficient operation to end Serb control of the western Slavonia area. Ending Serb control in the rebel republic of Krajina would be a much tougher proposition but, judging by Croat successes last week east of Knin, might not be impossible.

The regular Croatian Army, the HV, is estimated to number up to 110,000 by the UN though British intelligence puts their numbers more conservatively, at 70,000.

As part of the their moves to strangle Krajina, the Croats, including the Bosnian Croat militia, the HVO, probably intend to link up with the encircled Bosnian government forces in the Bihac pocket which have already been receiving aid from Zagreb.

Bihac is the most complex of wars. The Bosnian government forces (BiH) in the pocket are under attack from the east by Bosnian Serb forces, part of the 75,000-strong BSA; from the west by the Army of the Republic of Serb Krajina (Arsk); and from the north by rebel Muslim forces loyal to the local warlord Fikret Abdic - called the Army of Western Bosnia. Any heavy weapons the Abdic rebels have are probably loaned by the Arsk.

The most powerful forces in the region are those of rump Yugoslavia - the Yugoslav National Army, controlled by Serbia proper. This force has up to 90,000 troops but, more importantly, 1,300 tanks, 2,000 artillery pieces and 1,200 armoured fighting vehicles.

All the local forces are organised in corps - roughly 10,000-strong, subdivided into brigades which can vary from 1,000 to 3,000.

Throughout the three-year war the Bosnian Serbs have shown greatest mastery of warfare, especially the coordination of the movement of separate corps. But recently the Bosnian government forces have become increasingly professional and better organised. They are still very short of heavy weapons but have adapted their tactics to their circumstances and become a superb light infantry army. They have also benefited from the increasing war-weariness of the Bosnian Serb forces, thinly spread and short of men.

The seventh force in the Krajina-Bihac area, and the eighth in the region, is the United Nations. The UN Protection Force's new Rapid Reaction Force now has troops deployed from Tomislavgrad to Mount Igman to protect the supply routes into Sarajevo and unloading at Split.

In Croatia other UN forces are trying to monitor and observe military forces in Krajina and other disputed areas of Croatia. In the last few days their freedom of movement has been restricted, making it difficult for them assess any local activity. If the Croatians do move against the Krajina Serbs, the UN would be powerless.