Regional Outlook : A Nation Divided Faces Its Most Crucial Hour : Afghan factions are heavily armed, fiercely independent. They must choose between alliance or possible oblivion.

During the months that Afghan President Najibullah’s inner circle quietly engineered his overthrow, forces loyal to the most fundamentalist Islamic rebel leader in the country have been fighting in the strategic border mountains just west of Pakistan’s Khyber Pass, not with rifles and rockets, but with shovels and the words of the Holy Prophet Mohammed.

The holy warriors of Mecca-educated rebel leader Abdul Rasul Sayyaf have been busy digging underground fortresses, matching to the last detail those described more than 1,300 years ago in the holy book, the Koran. And quietly, they have been filling them with millions of dollars worth of sophisticated arms and ammunition.

To the south, in the strongholds of another fundamentalist rebel leader, the competing guerrilla forces of Gulbuddin Hekmatyar have transformed big, ancient caves into mammoth arsenals, stuffing them to the brim with state-of-the-art weaponry that include tanks, artillery and U.S.-supplied, heat-seeking Stinger surface-to-air missiles capable of downing aircraft flying at up to 20,000 feet.

In the north of the country, along Afghanistan’s strategic border with the former Soviet republics of Tajikistan, Uzbekistan and Turkmenistan, militias numbering in the tens of thousands have taken sole possession of huge depots of weaponry left behind by the Red Army when it finally went home--enough firepower to equip entire armored divisions, and including the same generation of Soviet-made Scud surface-to-surface missiles that Saddam Hussein fired at Israel last year.

Finally, as the bottom fell out from under Najibullah last week, regime commanders at the nation’s most strategic air base cut a deal just 30 miles north of Kabul, sharing control with major rebel factions over several squadrons of fully armed SU-22 and MIG-21 fighter jets.

This is the stage now set for Afghanistan’s most crucial hour--a turning point at which the world’s most war-ravaged nation is forced to choose either a tenuous and home-grown recipe for peace or a path leading to almost certain disintegration.

With the country’s strongman president finally driven from office, Afghanistan’s many armed factions--most of them now more deeply divided along ethnic than religious lines--will either talk to one another or resume their fight to the finish of the nation.

Since Najibullah’s ouster by leaders of his own army and ruling party, the regime’s tattered remains have been cobbling together a loose rainbow coalition to run Kabul with the backing of the most popular and dynamic rebel leader, the legendary “commander of the north,” Ahmed Shah Masoud.

And they have appealed to the better-armed fundamentalist factions led by Hekmatyar and Sayyaf to join them in a broad-based Islamic government in Kabul patterned after similar rebel-regime coalitions that have taken power in several major Afghan cities in the days since Najibullah fell.

A U.N. plan, touted only two weeks ago as Afghanistan’s last chance for peace, has been totally eclipsed by developments.

It would have begun with an emergency, 15-member interim council of “non-controversial Afghan personalities” taking power after Najibullah’s departure. The council was to rule for 45 days while a U.N.-sponsored gathering of prominent and largely impartial Afghans, held on neutral soil, selected an interim government to take over from the council until national elections could be held in 1993.

Now the United Nations and the Cyprus-born Armenian who is its special envoy on Afghanistan, Benon Sevan, are working urgently to help the emerging new moderate coalition forge an alliance with the Pushtun fundamentalists.

“If Afghans want to have a moujahedeen government, this is their choice. . . . There seems to be wide support for this idea,” Sevan told reporters Monday.

The real power center, however, is Masoud, 39. An Islamic revolutionary who wants to change the face of a nation long ruled by monarchies and Communists, Masoud is considered a relative moderate, known for his willingness to compromise. His expected talks this week with other rebel commanders may be critical in forging this Afghan-style alliance of regime, rebel, and even fundamentalist forces.

Although seemingly remote, the formula for national peace through an emerging network of autonomous, coalition-led islands of regional tranquillity--key cities where the fighting already has stopped, like Herat, Gardez, Mazar-i-Sharif and Kandahar--remains a possible alternative to Afghanistan’s looming anarchy even if the fight for Kabul itself resumes.

Hekmatyar on Monday gave the government until April 26 to either capitulate or face attack.

“No one knows the real military strength of Hekmatyar, but it’s just possible he’ll realize there’s no percentage in going against a new combined force of regime troops and guerrilla veterans,” said one European Afghan expert in Kabul. “For Sayyaf, it’s the same thing.

“Despite their ethnic differences from the coalition struggling to hold power in Kabul, the fundamentalists may not want to go it alone all the way.

“So, if this coalition succeeds in Kabul the way it has elsewhere, if it keeps the situation under control for a while, it will be all right.

“But even then, down the road, everyone will realize: ‘Hey, I am Tajik’ and ‘Hey, I am Pushtun,’ and then we can expect trouble.”

It is that ancient and geographical divide between Afghanistan’s long-ruling Pushtun majority and the large Tajik minority, which nevertheless now predominates in the Kabul coalition, that is the major factor behind predictions of an Afghan disaster--an all-out civil war between north and south in a nation where 13 years of largely ideological warfare already have left a million dead and 5 million refugees.

Such a civil war would have enormous implications for all of Central Asia.

Watching the events in Kabul with deep concern are the newly independent nations that emerged from the breakup of the Soviet Union--all of them under the control of moderate, secular leaders deeply fearful of an Islamic fundamentalist takeover in Kabul that could ignite similar passions among their own Islamic majorities.

“These governments fear that anarchy in Afghanistan would bring a new influx of refugees into the neighboring (former Soviet) Central Asian republics and fuel fundamentalist movements there,” said Sardar Aseff Ahmed Ali, a top Pakistani official who recently toured the area.

Pakistan, too, has a newfound interest in a stable Afghanistan. After serving as the conduit that funneled billions of dollars worth of U.S.- and Saudi-financed arms to the rebel moujahedeen in an effort to install a friendly Islamic regime in Kabul, Islamabad has a new economic imperative--export markets in the newly independent Central Asian nations of the former Soviet Union.

The road from Pakistan and its warm-water port in Karachi to the Central Asian hub of Tashkent passes directly through Kabul, and officials such as Deputy Finance Minister Sardar Aseff foresee billions of dollars in new trade opportunities, provided Afghanistan is at peace.

Iran, which shares Afghanistan’s western border, has its own economic imperative. Although publicly urging a peaceful solution to the brewing civil war, Tehran has it own road links with Central Asia and even more ambitious plans for future trade with the region than Pakistan, which it views as a potential competitor.

What’s more, the rebel-regime military coalition that took power over the weekend in Herat, the closest Afghan city to Iran, is made up largely of ethnic Shiite Muslims and factions that took refuge for years in Iran. Most Afghans are Sunni Muslims.

“The Iranians have nothing to lose and a lot to win, no matter what happens in Afghanistan,” said one Asian diplomat in the region.

But the agendas of Afghanistan’s neighbors are likely to play a minor role in resolving the crisis in a nation that, through the centuries, has stubbornly resisted invasions by Alexander the Great, the British, and a modern Soviet armed force that stayed for a decade until the rebels helped drive them out.

“The point is, the Afghans have always said they must settle this themselves,” the Asian diplomat added. “And when you look at Sayyaf’s underground fortress, Gulbuddin Hekmatyar’s arms depots, . . . ethnic groups that are now pitted against ethnic groups, and the national army’s loyalty in question everywhere in the country--well, you have to worry a lot about just how they really plan to do that now.”

Afghanistan’s fiercely independent ethnic groups are culturally and linguistically different peoples who have long mistrusted each other and coexisted largely on the basis of regional autonomy.

Although there has never been a reliable census in Afghan history, it is widely believed that the Pushtuns represent a narrow majority nationwide. They predominate in the eastern and southern regions that border Pakistan, where they speak their own language and live by a strict and ancient code, known as Pushtun Wali, that was laid down by their nomadic forefathers.

The ousted Najibullah is Pushtun. So is fundamentalist rebel leader Hekmatyar.

It is in the strategic northern provinces of the country that the Persian-speaking Tajiks, who represent an estimated 35% of the nation’s population, have made their stand and taken total military control in recent weeks.

In alliance with smaller minorities of Uzbeks and Turkomans, regular army and militia divisions principally under Tajik command openly rebelled against Najibullah last February, later joining forces with several key Tajik leaders of Najibullah’s own ruling party in Kabul. They now control the entire strategic border with the former Soviet Union.

What’s more, the rebel commander who emerged as the most charismatic and effective Islamic guerrilla leader during the war--Masoud--is an ethnic Tajik.

There is yet another key Afghan minority, the Hazaras. While representing less than 10% of the population, they are in their largest numbers in central Afghanistan and along its northwestern border with Iran. Almost exclusively Shiite Muslims, many of the Persian-speaking Hazaras look to Tehran for spiritual and political guidance.

As a U.N. source put it recently in assessing the regional implications of an Afghanistan dismembered along ethnic lines: “The Iranians have nothing to lose and a lot to win, particularly if the Hazaras break off and join them.”

The geographic equation is most complex in the capital city of Kabul--a sprawling kaleidoscope of mud houses and crumbling Stalinesque structures now filled with hundreds of thousands of refugees from a war that decimated villages nationwide. The influx of Persian speakers from Tajik and Uzbek villages that were leveled by Soviet bombing runs in the north has been so heavy that it has left the Pushtuns a minority in the capital.

The mountains of the Hindu Kush that surround the capital are controlled by ethnic Pushtun forces, who are, in turn, virtually surrounded by an outer ring of non-Pushtun armed groups.

“The biggest fear in Kabul right now is precisely that delicate, geographic balance of ethnic terror,” said the Asian diplomat, who has analyzed the war from inside Kabul for several years. “If street fighting breaks out in the capital, there’s nothing standing in the way of all-out civil war.

“The ethnic divide has always been there. The only difference now is that they’re all armed to the teeth.”

Afghanistan’s Patches of Power Afghanistan is a patchwork of ethnic territories whose leaders are jockeying for power in the turbulent nation. Pushtuns, with ties to Pakistan, rule the southeast. Their main rivals are the Tajiks, controlling the north in alliance with ethnic Uzbeks and Turkomans. Hazaras, a small but influential group, look to Iran for guidance. They control much of central and northwestern Afghanistan. PRESIDENT NAJIBULLAH * Fallen president and former head of dreaded, Soviet-style secret police. * Elevated to presidency by Moscow in 1986, the peak of Soviet occupation. * An ethnic Pushtun. Brn Najib Ahmadzai in the eastern border regions of Kunar province. * Shrewd, a master of manipulation and resilient, surviving three years of internal plots and coup attempts since Soviets’ 1989 troop withdrawal. * Powerfully built and brutal with his enemies, he is nicknamed “the Ox.”

ABDUL RASUL SAYYAF

* Heavily backed financially and militarily by Saudi Arabia. * Leader of Wahabbi, a tiny Arabic-speaking sect in the east. * Well-armed. Vehemently anti-American. * Favors fundamentalist Islamic government in Kabul. * First rebel leader to reject U.N. peace plan. His forces likely to try any military action to torpedo it.

GULBUDDIN HEKMATYAR

* Most influential and best-armed of seven major moujahedeen rebel factions. * Virulently anti-Western. * Eloquent speaker, brilliant strategist and charismatic leader of his Hezb-i-Islami, or Islamic Party. * Throughout much of Afghan war, he got majority of CIA-supplied weaponry. Since Soviet pullout, U.S. has tried to stop arms shipments. * Ethnic Pushtun, with strong support in eastern provinces that border Pakistan.

BAHARUDDIN RABBANI

* Leader of Masoud’s Jamaat-i-Islami. * Has less militant approach to converting Afghanistan into Islamic state. * Backs infiltration of regular army to plant seeds for Islamic counterrevolution. * Ethnic Tajik. Widely respected by Tajiks even within army that he has fought so hard to defeat. AHMED SHAH MASOUD * Most charismatic and committed of moujahedeen field commanders. * Known for moderate interpretation of Islamic law. * Ethnic Tajik who has wide civilian and military support. * His guerrillas liberated a vast tract of land praised as one of few regions where development has been possible. * Affiliated with Pakistan-based Jamaat-i-Islami Party. * Skirmishes between Masoud’s largely Tajik forces and Hekmatyar’s Pushtun followers seen as ill omen for nation’s future.