Two months of fighting for the strategic city of Jalalabad has demonstrated the unexpected tenacity of the Afghan armed forces and exposed weaknesses in the divided guerrilla opposition.

Each day the Soviet-backed government holds the provincial capital, the more confident it becomes it can withstand a guerrilla siege and force the insurgents and their Western supporters to negotiate peace.For nearly 10 years, the guerrillas - known as mujahedeen - waged their holy war against the Soviet army, which entered Afghanistan in 1979 to prop up the Marxist government. The enemy was an invading superpower to them and the battle lines were clear.

But now the Soviets are gone, and the guerrillas have come down from the mountains to the rocky plains of Jalalabad. They are trying to move from hit-and-run attacks to full-scale conventional warfare in the largest and bloodiest offensive of the 11-year civil war.

So far, neither side is winning.

Diplomats in Kabul have said 7,500 to 12,500 insurgents and government soldiers have died or been wounded during the eight-week siege. There are no estimates on casualties among Jalalabad's civilian population, which once numbered about 64,000.

The guerrillas have pounded the eastern city with as many as 16,000 rockets a day. The forces of President Najib have responded with long-range Scud missiles and have dispatched MiG-21 and MiG-27 jets to pound guerrilla camps.

Jalalabad and its magnificent gardens and palaces has been virtually destroyed. Refugees are fleeing the carnage by foot and on flatbed trucks.

The mujahedeen are fighting as fiercely as ever but with little coordination or military discipline.

Meanwhile, government forces have proved they can fight effectively without Soviet troops to back them up. The soldiers are driven in part by fear of death or torture if captured by the insurgents.