Ukraine's fighting spirit will bleed Russia's military dry, a U.S. Special Forces veteran told Fox News.

"I look at the unconventional warfare or the fight that's happening there, and I think you're going to see a lot of guerrilla warfare coming soon," U.S. Army retired Lt. Col. Scott Mann said. 

"These cities are going to get overrun, and it's going to be a long, long haul for the Russians," Mann continued. "If they think because they occupy these cities, that they're done – if you look at the fighting spirit of the Ukrainian people – they are in for a nasty guerrilla warfare campaign that is going to bleed them dry."

In this image taken from footage provided by the Ukrainian Defense Ministry Press Service, a Ukrainian soldiers use a launcher with US Javelin missiles during military exercises in Donetsk region, Ukraine, Wednesday, Jan. 12, 2022. The Russian invasion of Ukraine is the largest conflict that Europe has seen since World War II, with Russia conducting a multi-pronged offensive across the country. The Russian military has pummeled wide areas in Ukraine with air strikes and has conducted massive rocket and artillery bombardment resulting in massive casualties. (Ukrainian Defense Ministry Press Service via AP, File) (Ukrainian Defense Ministry Press Service via AP, File)

The retired Green Beret commander told Fox News the situation in Ukraine is unfolding opposite to the way things played out in Afghanistan.

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"I’ve got to think that the Taliban are not liking what's going on in Ukraine right now," Mann said. "People are watching that and it is inspiring, regardless of your politics, to see people make a stand like that."

Mann, who served in Iraq and Afghanistan, founded Task Force Pineapple, a group that helped evacuate Afghan refugees after the country fell into the hands of the Taliban last year.

Lt. Col. Scott Mann (Ret.) with Nesam (Courtesy: Task Force Pineapple)

The group is not involved in Ukraine because, according to Mann, the circumstances are different.

"Even though it is horrific warfare, you have kind of a linear battlefield, and you have nation states," said Mann. "I think volunteer groups, we have to be really careful about how we engage here and what we do."

Mann equated the final days of the Afghanistan withdrawal to the "wild, wild west." He said Pineapple came together because of his team’s specific knowledge of the country, which wouldn’t translate in Ukraine.

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He told Fox News there are three reasons why the war in Ukraine is unfolding differently from the fall of Afghanistan. 

Zelenskyy

KYIV, UKRAINE - FEBRUARY 25: (EDITORIAL USE ONLY  MANDATORY CREDIT - "PRESIDENCY OF UKRAINE/ HANDOUT" - NO MARKETING, NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS)  Ukraine's President Volodymyr Zelenskyy holds a press conference on Russia's military operation in Ukraine, on February 25, 2022 in Kyiv. (Photo by Presidency of Ukraine/Handout/Anadolu Agency via Getty Images) ((Photo by Presidency of Ukraine/Handout/Anadolu Agency via Getty Images))

"The first one is leadership," Mann said.

"If you contrast just the internal leadership at senior levels inside Ukraine versus Afghanistan, it is stark," he continued. "You have the president of Ukraine saying ‘We don't need a ride, we need ammo,’ … ‘if you can't control the sky, give me planes,’ versus [then-Afghan President-Ashraf] Ghani and his staff scrambling for helicopters unannounced to flee and leave their people high and dry."

Ukraine’s embrace of nationalism is the second, according to Mann.

"Ukraine has a national identity, and it runs deep, and they fight for it," Mann told Fox News. 

"Afghanistan historically has not been as keen on a national identity," he continued. "It's primarily a status society, a tribal society."

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"The final one is the nature of the threat," he said.

"If you look at Ukraine, they're facing an external threat," Mann continued. "Nothing unifies people more than an external threat"

"It brings us together fast, whether it's a hurricane or the Russian bear," he said. "Whereas with the Taliban, that was an internal threat, that was a long-term insurgency that, you know, really applied a thousand cuts to the Afghan government."