He promised an "organized resistance" to Taliban rule. Now he wants U.S. help to lead the fight.
While the Taliban's dramatic takeover of Afghanistan was met with little resistance, clear signs of defiance were appearing on Thursday.
In an op-ed published in The Washington Post, the son of Afghanistan's most famed anti-Taliban fighter claimed to have the forces to mount an effective resistance, but he called on the United States to supply arms and ammunition to his militia.
"I write from the Panjshir Valley today, ready to follow in my father's footsteps, with mujahideen fighters who are prepared to once again take on the Taliban," Ahmad Massoud said, adding that "America can still be a great arsenal of democracy" by supporting his fighters.
In Moscow, Russian Foreign Minister Sergei Lavrov said Thursday that a Taliban resistance was forming in Afghanistan led by ousted Frist Vice President Amrullah Saleh and Massoud.
"The Taliban doesn't control the whole territory of Afghanistan," Lavrov told reporters.
On the political front, the Taliban continued to edge toward establishing a government, meeting with senior Afghan figures from the past two decades.
Taliban negotiator Anas Haqqani met with Hamid Karzai, the first Western-backed leader of Afghanistan after the Taliban's ouster in 2001, and Abdullah Abdullah, who had led the government's peace council, the militant group said on Twitter.
Saleh and Massoud were prepared for the coming fight. On Tuesday, after President Ashraf Ghani fled abroad, Saleh made it clear that he was staying in Afghanistan, and he declared himself the "legitimate caretaker president" of the country.
When he was still part of the serving government in May, Saleh told CBS News' Charlie D'Agata that the U.S. was wrong to have entered into negotiations with the Taliban in the first place, saying the group could not be trusted. He indicated then that if the militants were "waiting for a moment of surrender from the Afghan people, it won't come."
Many of the country's security forces did walk away from their posts without a fight in the face of the Taliban's rapid return to power, but Saleh and Massoud appeared set to challenge the notion that the entire country would fold as easily.
Massoud and his followers have been preparing for a possible all-out civil war for months, even as they hoped the situation wouldn't get that bad.
"I'll fight for it, and I'm ready to give my life for it," he told D'Agata in May. His father gave his life for it: Ahmad Shah Massoud was a renowned guerrilla commander who led the resistance against the Taliban occupation in the 1990's.
The senior Massoud was assassinated just two days before September 11, 2001. The Taliban knew the U.S. would retaliate for the terror attacks, and the anti-Taliban commander would have been too dangerous an ally to allow the Americans.
His son told CBS News in May that he and others were ready to take up arms in what some had already started calling "Resistance 2.0."
"Armed groups against international terrorism," he told D'Agata. "They are ready. If the situation goes towards a war, we will announce it, and we will be ready."
"It will be people ready to fight," he said. "It will be an organized resistance against the Taliban."