Ismail stands astride a massive motorcycle that mutters in neutral. With his thick mustache, lantern jaw and wavy black hair flowing past his shoulders, he looks set to play in a Hollywood movie about the Hell's Angels.

But, at 28, Ismail is an ex-farmer, now second in command at this markaz, or guerrilla base, of the National Islamic Front of Afghanistan in northern Ghazni Province. Ismail is neither a landlord, nor a member of an elite family, nor a religious authority figure; traditional Afghanistan would not have called him from his farm to be a leader -- especially not at his age.

But traditional Afghanistan is eroding under the pressures of more than six years of Soviet occupation, and, inside the country, the leadership of the young is perhaps the most obvious evidence of this society's forced evolution. Here, where age always has been a main criterion for leadership, the dozen field commanders encountered during a recent trip had an average age of 31, and none was older than 40.

According to the other mujaheddin here, Ismail is a leader because he is courageous and because he learns quickly how to use weapons and solve the problems of their continuing battle with Soviet troops based in the nearby town of Ghazni.

"I was a poor man," said Ismail, "and I never went to school. But I learned by myself how to read and write -- and any weapon I see, I try to learn it as quickly as possible."

Various young commanders interviewed during the one-month visit to Afghanistan said the burden of leadership inside the country has shifted to them because of the mental -- and physical -- challenges of the war.

"We can't fight by pushing buttons," said Kabul commander Abdul Haq, in his late twenties. "We fight by walking for days, and with no food and in the snow," he said. "Our fight is for young men."

According to another mujahed leader, Ruhani Wardak, 24, "when the war began, many of the older, traditional leaders were in charge at first, the religious leaders and tribal chiefs."

"But the younger men were best at learning what we had to do to fight the Soviets with their tanks and helicopters," he said.

The shift in leadership on the battlefield has not changed the Afghans' traditional respect for age. Within the guerrilla bases, young commanders were unfailingly respectful to the older men they led -- but the commanders' authority was never questioned.

Many of the traditional leaders of Afghanistan's villages, the tribal chiefs and landlords, were chased from their homes under the Afghan Communist governments that preceded the Soviet invasion. Now, authority in the villages is often shared among the young commanders and the older men who remain.

In this region, there are few young men left in the villages, most having gone to the guerrilla bases or to neighboring Pakistan to seek work. In the villages, the authority of the elders remains strong -- but local residents said in cases of disputes among such older men, or between villages, a local commander might be asked to arbitrate.

Virtually all the commanders interviewed insisted that they continue to rely on the older leaders for direction and that their own influence would not eclipse that of the traditional elite. In the villages, the need for cooperation between influential elders and the young commanders was clear: The mujaheddin, like any guerrilla movement, rely on the population for material support and information.

The commanders inside Afghanistan also depend on the leaders of the Afghan political parties, based in Peshawar, for weapons and supplies. Most party leaders are older men, with traditional religious or hereditary claims to leadership.

Western observers and many mujaheddin agree that influence and authority in the resistance are shifting gradually from the older and more ideological elites represented by the party leaders to the younger and often more pragmatic battlefield commanders.

Amin Wardak, older brother of Ruhani, says the commanders have remained in closer touch with Afghans in the country than have the party leaders -- and will press increasingly for a role in the broader leadership of the movement. Just over a century ago, when an earlier generation of Afghans fought an invading British army, one of Amin Wardak's forbears, Mohamed-Djan Wardak, led the fight on the battlefield but then relinquished any claim to power.

"That is not going to happen this time," Wardak said.

A British anthropologist working inside Afghanistan, who asked not to be named, suggested that the commanders' pragmatism may help them increase their influence. "In the field, the commanders seem better able to cooperate in practical ways than the parties do politically," he said.

Also, the commanders "are more open to the outside and potentially are a bridge between the West and Afghanistan's conservative Moslems," he said. "But like the other changes in this country, it's difficult to predict the implications of something we can only partially see."