Based on recent Taliban activity, Taliban leaders might initially focus their operations on the capitals of such provinces as Helmand, Kandahar, Ghazni, Farah, Uruzgan, Kunduz and Zabul. As in previous campaigns, the Taliban would likely lay the groundwork for offensive operations months in advance. They might conduct targeted assassinations of government, tribal and other influential individuals that support the government, as well as preposition fighters, weapons, material and supporters in strategically-important areas. The Taliban could then overrun nearby district centers and recruit additional supporters, collect taxes and plan for expansion. This includes using bases in these districts as staging areas for the eventual push into Afghan cities. They might also overrun nearby jails and release the prisoners, including Taliban prisoners, as they did in Ghazni in August 2018 and Kunduz in September 2015. Taliban fighters would then move into cities from positions in nearby districts, villages and suburbs by overrunning government checkpoints and bases, cutting off telecommunication links, blocking major highways and then seizing urban areas. The Taliban could then use these victories to eventually seize Kabul.

The Taliban has as many as 60,000 to 70,000 fighters, compared to approximately 312,000 Afghan army and police forces. If the Taliban can increase its control of populated areas and operate at a high tempo against an Afghan force roughly five times larger with U.S. support, as it is doing today, the Taliban will be able to expand its control of territory more quickly without U.S. forces. Among the Taliban’s most competent organizations, which it would use in attacking cities, is the Red Unit (or Sara Kheta in Pashto). It is an elite force that is better trained and equipped than ordinary Taliban forces. Some fighters from the Red Unit have sported Russian-made night vision goggles and American-made M-4 assault rifles equipped with laser pointers for effective sniper activity.

While it is likely that the Afghan government would eventually fall to the Taliban following a departure of U.S. military forces, it is unclear how quickly the Taliban would seize Kabul. After the withdrawal of Soviet forces from Afghanistan in 1989, the CIA predicted the imminent collapse of the Najibullah government: “We judge that Mohammed Najibullah’s regime will not long survive the completion of Soviet withdrawal even with continued Soviet assistance. . . The regime may fall before withdrawal is complete.” Other U.S. experts on Afghanistan predicted the quick overthrow of the Najibullah government by the mujaheddin. “Without the Soviets, it was believed, the Kabul government’s morale would plummet, the regime would disintegrate and the mujaheddin would sweep victoriously forward,” wrote Zalmay Khalilzad, the current U.S. diplomat and Special Representative for Afghanistan Reconciliation, in January 1990. But Najibullah was able to cling to power for several more years because of continuing Soviet aid and infighting between mujahideen factions.

The timing of Kabul’s collapse following a U.S. departure might depend on several variables. The first is whether—and to what extent—the United States and other international donors continue to provide military, financial and other aid to the Afghan government and anti-Taliban groups. In the six months following the Soviet withdrawal in 1989, for example, Moscow flew nearly 4,000 planeloads of weapons and supplies into Afghanistan and aided urban and rural militias. International aid could help stall the collapse of the government, but only temporarily. A second factor is the speed of deterioration of Afghan security forces. Afghan army and police units could fracture along ethnic and patronage lines, as units support local militia commanders. The quicker that Afghan government units disintegrate either because they defect to the Taliban or fragment into local militias, the quicker the Taliban will be able to seize and hold territory. A third factor is whether the Taliban faces a serious challenge from other groups, such as the Islamic State Khorasan Province, that force it to divert resources away from fighting Afghan army and police units.

In addition, the Taliban could face challenges in quickly controlling all of Afghanistan. The group’s ideology is too extreme for many Afghans—particularly urban Afghans—who adhere to a much less conservative form of Islam that permits most modern technology, music, political participation and some women’s rights. The Taliban have utilized brutal tactics, including bombings and suicide attacks that have killed civilians, which have led to widespread international condemnation and undermined its support in Afghanistan. Taliban suicide attacks have been especially devastating, killing thousands of Afghan civilians—including women and children—and maiming tens of thousands of others over the past decade.

The Taliban is also involved in widespread corruption and its track record in governing Afghanistan has been abysmal. According to data from the World Bank’s Worldwide Governance Indicators, the Taliban was the worst-performing government in the world during its reign. Its expansive involvement in virtually all aspects of the opium trade today indicates that it is becoming a major drug cartel, in addition to an insurgent group. Drug revenue accounts for over half of the Taliban’s total financing and is the single most important source of revenue for local commanders. Consequently, a Taliban victory would not likely be the end of conflict, even if the group successfully overthrew the government in Kabul.

Still, a Taliban overthrow of the Afghan government—or even control of significant portions of the country—would have several implications for U.S. national security. First, it would almost certainly be viewed by jihadist groups as a major victory. The Soviet withdrawal from Afghanistan in 1989 was a substantial source of inspiration and recruitment for Al Qaeda. Osama bin Laden used the Soviet defeat as a rallying cry and source of inspiration until his death. A U.S. withdrawal from Afghanistan could have a similar psychological impact for the global jihadist community.

Second, Afghanistan could become a terrorist sanctuary with a Taliban victory, including for groups like Al Qaeda in the Indian Subcontinent (Al Qaeda’s local affiliate), the Tehrik-e-Taliban Pakistan, Islamic State Khorasan, Lashkar-e-Taiba and other groups.

These groups can continue to enjoy a safe haven in Afghanistan even if the Taliban promised to break ties with Al Qaeda and other terrorists. If the Afghan and Pakistani governments have failed to eliminate Al Qaeda and the Islamic State from their territory, why would the Taliban be able to do it?

All of these groups have a presence in Afghanistan and have conducted or inspired attacks against the U.S. homeland, U.S. forces, U.S. government installations (such as embassies) in Afghanistan and Americans and other Westerners in nearby countries like India. Next to Syria, Afghanistan has the largest number of jihadist fighters and allies anywhere in the world—including compared to countries like Iraq, Pakistan, Libya, Nigeria and Somalia.

A Taliban victory would likely serve as a magnet for jihadists across the globe, who wished to live in a country governed by sharia (Islamic law) and were inspired by the Taliban’s successes. The group’s previous reign in Afghanistan, which lasted from 1996 to 2001, attracted Al Qaeda members and other extremists. Another era of Taliban rule would likely have the same result. Iraq after the U.S. withdrawal is illustrative: the Islamic State took advantage of the vacuum and seized significant areas in Syria and Iraq.

Third, a successful Taliban-led insurgency would deal a severe blow to human rights development in the country. The Taliban remain deeply opposed to women’s rights and would likely reverse progress in a country that has experienced a notable rise in the number of female business owners; female government officials; and primary, secondary and university students. Girls, barred from education under the Taliban, now account for 39 percent of public school students in Afghanistan. The Afghan Parliament has set aside sixty-nine of its 250 seats in the lower house for women, while the upper house includes twenty-seven female members of parliament out of its 102 members. Much of this would likely be overturned. In addition, a Taliban victory would almost certainly increase refugee flows out of Afghanistan. Afghan refugees are already the second-largest refugee population in Europe next to Syria, according to the UN High Commissioner for Refugees. This situation would almost certainly become worse if the current government falls to the Taliban.

Fourth, a Taliban victory could increase regional instability and security competition, as countries like India and Pakistan support a mix of central government forces, sub-state militias and insurgent groups. Afghanistan would further deteriorate into a proxy war among Afghanistan’s neighbors.

Based on the implications of a complete U.S. military withdrawal, Washington has several options, none of them favorable. The United States can withdraw all forces, but continue providing military and non-military assistance to the government and local actors. As the Soviet experience in the early 1990s illustrates, however, continuing outside assistance might only slow down—not stop—a potential government collapse.

Alternatively, the United States could keep a small counterterrorism force of several hundred or a thousand personnel in place as part of a phased withdrawal. U.S. special operations forces could work with the CIA, other intelligence agencies, NATO special operations forces, and high-end Afghan units like the Ktah Khas and Afghan National Army Commandos to capture or kill Al Qaeda, Islamic State and other terrorists. The United States might also utilize limited “enablers,” such as unmanned aerial vehicles and intelligence, surveillance and reconnaissance assets. But this option has substantial risks: U.S. forces would have little or no capabilities to assist the Afghan government in its war with the Taliban. With a major U.S. retrenchment that involved withdrawing most U.S. forces and enablers from Afghan provinces, the Taliban would likely conclude it could defeat Afghan forces militarily, overrun major cities and ultimately seize Kabul.