Pakistan's post-Afghan legacy. Moscow is showing new signs of displeasure with Afghan puppet leader Najibullah (right). But, even as a Soviet pullout appears more and more likely, Pakistan and the Afghan resistance are bracing for trouble of other kinds. Stories below and Page 7.

Pakistan faces a legacy of simmering troubles at home and new uncertainties along its borders in the event of a Soviet pullout from neighboring Afghanistan. The eight-year Soviet occupation has fueled a wave of lawlessness along the rough-and-tumble Afghanistan-Pakistan border: Black markets for weapons and heroin flourish. Partisan differences frequently flare up into open conflict. And even the return of 3 million Afghan refugees huddled along the frontier may only diminish, not end, the violence that has made the area almost ungovernable.

``It won't calm down overnight,'' says a Pakistani law enforcement official. ``The drug dealing, tribal tensions, and Kalashnikov culture may ease, but they won't die out.''

Efforts to bring peace to Afghanistan will also have an impact on Pakistan's volatile borders with Iran and India.

President Mohammed Zia ul-Haq's government has been careful to nurture good relations with Iran, which hosts about 2 million Afghan refugees. An Iranian refusal to cooperate with a Pakistan-Afghanistan peace settlement could rekindle old tensions over Pakistan's treatment of its Shiite Muslim minority and relations with the United States.

A settlement could also usher in a critical new era of South Asian rivalry.

Ostensibly, it would remove a major irritant between India and Pakistan, which have been at loggerheads over the 1979 invasion by the Soviets (with whom India has solid ties) and burgeoning US aid to President Zia's regime. (India and Pakistan have fought three wars since 1947.)

The Afghan troubles have kept Pakistan's animosity toward militarily superior India in check in recent years, Western and Pakistani analysts say.

``From India's point of view, they would be quite happy for Afghanistan to go on forever,'' observes a European diplomat in Islamabad. ``If the war ends, Pakistan's full attention will be on India. What that will mean in these countries' bitter relations remains to be seen.''

But now India is apparently shifting its stand on the Afghan issue - and raising new concerns here about its aspirations as a regional power. Though it refused to condemn the Soviet invasion, India recently sent an emissary to meet Zahir Shah, the exiled Afghan King, in Rome.

The visit, which diplomatic sources say was made at Soviet urging, was widely seen as an Indian attempt to nudge negotiations toward a compromise on a moderate Afghan government.

Islamabad is worried by these moves, analysts say, despite India's having little credibility with Afghans.

``India, for the last 8 years, has behaved in a manner which could not have earned them popularity with the Afghan people,'' says Zain Noorani, Pakistan's foreign affairs minister. ``They are trying to regain whatever credibility they have lost, not only among Afghans, but also among other countries....''

Pakistan will bear the burdens of war for years, political observers say. The thriving drug trade, which many Pakistanis blame on Afghan smuggling operations, feeds the habits of about 600,000 addicts here. It is also estimated to supply about one-third of all the heroin sold in Europe and the US.

Gunrunning is endemic. Of the millions of dollars worth of weapons supplied to the Pakistan-based Afghan resistance by the US, China, and Islamic donors, many have been siphoned off for tribal warfare. Border officials worry that once the Soviets are gone, the tribesmen - mostly ethnic Pathans who inhabit large tracts on both sides of the border - might turn the guns on one another or on law enforcement officials.

The parallel economies of guns and drugs have handsomely profited many civil and military officials, critics of the Zia government claim.

Much of the crime, so far, has centered in the North-West Frontier Province.

``The problems [in the frontier] have been contained and cushioned by foreign aid,'' says political commentator Ayaz Amir. ``But if that foreign aid pipeline is choked off, then many Pakistanis will start feeling the effects of it.'' Mr. Amir was referring to the flood of foreign aid that has helped support the economy and defray the cost of providing for Afghan refugees.

There is growing Pakistani resentment in border areas over Afghans who have taken away jobs or taken control of vital sectors such as transport. And the desire to ensure that most, if not all, Afghan refugess return is key to Pakistan's recent insistence that the details of a coalition government be worked out before it signs an accord with Soviet-backed Kabul regime.

During most of the six years of UN-sponsored negotiations, Pakistan has said the formation of an interim government should be left to the Afghans to decide after a Soviet withdrawal. But now many officials say an interim arrangement is needed to prevent a bloodbath and renewed chaos along the border.

``The withdrawal of Soviet troops from Afghanistan without an interim agreement on an interim government could trigger a civil war and further destabilize the region,'' says Fida Mohammead Khan, governor of the North-West Frontier. Pakistan has long feared the growth of a separatist tendency among the Pathans in the region.