Lt Gen Sami Sadat said that eight months of Taliban rule has convinced many Afghans that military action is the only way forward.
He said operations could begin next month after the Islamic Eid festival, when he plans to return to Afghanistan.
The Taliban took control of the country in a rapid offensive last August.
The hard-line Islamists swept across the country in just 10 days, as the last US-led Nato forces left following a 20-year military campaign.
Speaking for the first time about the plans, Lt Gen Sadat told the BBC he and others would "do anything and everything in our powers to make sure Afghanistan is freed from the Taliban and a democratic system is re-established".
"Until we get our freedom, until we get our free will, we will continue to fight," he said, while refusing to be drawn on a specific timeline.
The general underscored how the Taliban had been reintroducing increasingly harsh rule - including severe restrictions on the rights of women and girls - and it was time to stop their authoritarian order and start a new chapter.
"What we see in Afghanistan in eight months of Taliban rule has been nothing but more religious restrictions, misquotation, misinterpretation and misuse of the scripts from the Holy Koran for political purposes."
He initially planned to give the Taliban 12 months to see if they would change, he said. "Unfortunately, every day you wake up the Taliban have had something new to do - torturing people, killing, disappearances, food shortages, child malnutrition."
He said he received hundreds of messages daily from Afghans asking him what he was going to do about it.
But in a country shredded by more than 40 years of conflict, many Afghans are weary of war, desperate to leave, or struggling to survive in the midst of a deepening economic crisis. The UN speaks of a country marked by "combat fatigue" with millions on the brink of starvation.
Many in rural areas which bore the brunt of Nato's war against the Taliban have welcomed the relative calm now that US and Afghan warplanes have left the skies and Taliban attacks have ended.
Lt Gen Sadat, who commanded Afghan government forces in the southern province of Helmand in the last months of the Taliban offensive, is also accused of ordering attacks which killed civilians. When questioned about the charges he denied them.
In August last year he was appointed to head the Afghan special forces and arrived in Kabul the day the Taliban swept in and his commander-in-chief President Ashraf Ghani fled the country.
Asked whether there was any alternative to another war, Lt Gen Sadat said he hoped that moderate Taliban, known to be uncomfortable with a growing raft of restrictions reminiscent of draconian Taliban rule in 1990's, could be part of a new government.
"We are not against the Taliban," he said, just against their current "textbook," describing an Afghanistan where "everyone fits in, not a country only for Taliban."
In recent weeks, an audio message in which the general speaks about an armed fight against the Taliban with the aim of "re-liberating" Afghanistan was leaked to the media.
In the past, armed groups including the Taliban won Afghan wars with the support of neighbouring countries, a foothold in the country, and foreign funding.
It is not clear that Lt Gen Sadat's allies, as well as the many other armed groups which have been forming, have any of these assets.
Multiple groups are now united by their goal of ousting the Taliban but they're also divided along ethnic lines, and loyal to rival commanders.
Lt Gen Sadat said he was in touch with one of the most prominent groups known as the National Resistance Front (NRF) whose leading figure is Ahmad Massoud, son of the late legendary commander Ahmad Shah Massoud.
"I am in contact with my brother Ahmad Massoud and we support his actions in every way, I also contact and support other resistance groups," he said in his leaked message.
He told the BBC their fight was an insurgency funded by patriotic Afghans. He said they had no foreign backers and were not seeking one. At 37, the former army's charismatic and youngest general - who was educated in London and many western military academies - said his generation recognised that mistakes were made by the past administration he was part of.
But he said they were let down by corrupt Afghan politicians and US policies.
He believed, he said, that the chaotic US troop pullout in Afghanistan had shown America's weakness and led to Russian President Vladimir Putin's decision to invade Ukraine.
There was criticism of the chaotic US-led Nato pullout from the country, with questions raised over how the Taliban was able to seize control of the country at such speed.
Lt Gen Sadat said it was bad for Afghanistan but he blamed it on politicians in Nato countries, most of all US President Biden, not western military commanders, many of whom he is still in touch with. "It's not an ending that we could be proud of, or happy with."
He expressed admiration for Ukraine's resistance but warned that they too could one day be let down by Nato.
"I think they are holding their ground pretty well. But I also tell them to, you know, believe in themselves more, because the continued support from Nato and other countries could come to a halt.
"I hope they will get continued support as long as they need it."