The Taliban have yet to capture all of Afghanistan. A province has promised to resist

(CNN) – As the Taliban tighten their grip on Afghanistan, there is a remote region whose resistance to the militant group dates back decades. Now the last great stronghold is under threat.

The Taliban have been concentrating forces in and around Panjshir province, the only province that has still fallen under militant control. On Monday, the Taliban said they had captured three districts in the Panjshir Valley.

Here’s what you need to know about the resistance movement in Panjshir.

Where is the Panjshir Valley?

The Panjshir Valley, about 150 kilometers north of Kabul, is the epicenter of Afghan guerrilla warfare.

The valley has long resisted foreign occupation; the army of the British Empire was unable to penetrate the region during its attempt to take Afghanistan in the 19th century.

In the 1980s, fighters defending the valley under the leadership of Ahmad Shah Massoud managed to keep Soviet forces at bay, even as the USSR controlled Kabul and large swaths of the rest of the country.

The landscape of the Panjshir Valley plays a role in his defensive success. Hidden in the Hindu Kush mountain range and accessible only through a narrow gorge, local forces have long used its remote location as an advantage over would-be invaders.

Before the Taliban took control of Afghanistan, the leaders of Panjshir province had asked the Afghan government in Kabul to grant them more autonomy.

The majority of the valley’s population are ethnic Tajiks, while the Taliban are primarily Pashtuns.

Who are the Northern Alliance?

After the Soviets withdrew from Afghanistan in 1989, various factions of mujahideen, or Islamic holy warriors, split into groups, fighting for control of the country.

Out of this chaos, Massoud formed the Northern Alliance, a coalition of Uzbek and Tajik forces. For a time, his forces occupied Kabul, but were accused of human rights abuses.

Most of the country fell to the Taliban in 1996. But the Northern Alliance, under Massoud’s leadership, managed to keep the Panjshir Valley free from the militant group’s control during its five years of rule.

Known as the “Lion of Panjshir,” Massoud led an offensive against the Taliban until he was assassinated by members of Al Qaeda two days before the September 11, 2001 attacks. CNN national security analyst Peter Bergen called the incident as “the backdrop to the attacks on New York City and Washington that followed.”

The coalition is now led by Massoud’s son, Ahmad Massoud, who has vowed to continue the fight against the Taliban in the wake of their near-takeover in Afghanistan.

In an editorial by The Washington Post Last week, Massoud, 32, appealed to Western forces for help in that fight, saying that Afghan army soldiers, including some of the elite Special Forces units, had joined the cause.

“We have supplies of ammunition and weapons that we have patiently collected since my father’s time, because we knew this day would come,” he wrote. “If the Taliban warlords launch an assault, they will of course face stiff resistance from us,” he said.

Former Afghan Vice President Amrullah Saleh, who was born in Panjshir and trained there before eventually leading Afghanistan’s intelligence agency, fled to Panjshir after Kabul fell to the Taliban.

But the playing field has changed rapidly, with the mountainous area north of the capital now infiltrated by Taliban forces, blocking crucial supply lines to the region.

Wazir Akbar Mohmand, a former Afghan National Army major who joined Panjshir’s opposition, said in a tweet on Monday: “Snipers, road blocking artillery position and 20,000 soldiers ready to fight.”

On Saturday, French writer Bernard-Henri Levy, who has long been a supporter of the Northern Alliance, tweeted: “I just spoke to Ahmad #Massoud on the phone. He told me: ‘I am the son of Ahmad Shah Massoud; surrender it’s not part of my vocabulary. ‘”

Will Panjshir fall to the Taliban?

On Monday, the Taliban claimed to have captured three areas of the Panjshir Valley from the Northern Alliance, and Taliban spokesman Zabihullah Mujahid tweeted that “Banu, Bel Hisar and De Salah districts were completely cleansed of evil.”

Over the weekend, the Taliban moved reinforcements into the region, calling on the Northern Alliance and its leader to surrender.

“Mujahideen from Badakhshan, Takhar and Baghlan states are now stationed at the gate of Panjshir,” Zabihullah said.

He denied Saleh’s claim that the strategic Salang pass had been blocked, saying that it was open and that “the enemy is besieged in the state.”

The Taliban spokesman also said: “The Islamic Emirate seeks to resolve the crisis peacefully.”

Another Taliban spokesman, Suhail Shaheen, said: “Conquering Panjshir by force will be the last option, as it is against our policies. We will do our best not to go down that path.”

In an interview with Reuters on Sunday, Massoud said he was open to negotiations as long as the Taliban promised an inclusive government, but that his supporters were willing to fight if the Taliban tried to invade the valley.

“They want to defend, they want to fight, they want to resist against any totalitarian regime,” Massoud said.

Elders from Panjshir have been in Kabul in recent days exploring possible engagements. But so far his efforts have been unsuccessful.

On Sunday, a spokesman for the Massoud National Resistance Front (NRF) said they believe a decentralized government was the “only solution.”

“We are in favor of peace, but peace does not mean surrendering to the demands of the enemies and having one force dominate the politics of the country. Our conditions for a lasting peace in Afghanistan are the decentralization of power and wealth, democracy, politics and cultural pluralism, moderate Islam and equal rights and freedom for all citizens, “NRF spokesman Ali Nazary told CNN.

Nazary added that the NRF believes that the “threat of international terrorism is increasing and will once again threaten the interests and soil of the United States.” He called on the West to “cooperate with the NRF, to prevent another 9/11 from happening.”