- Russia's offensive against Ukraine comes eight years after it seized Crimea and stoked a separatist movement in eastern Ukraine.
- Since that 2014 invasion, US and Western special-operations forces have trained Ukrainian troops to conduct unconventional warfare.
- Should the conventional fight in Ukraine end in Russia's favor, Ukrainians could put those unconventional skills to use.
The invasion of Ukraine isn't going as planned for Russian President Vladimir Putin. Days into the operation, his forces are struggling to meet their objectives and facing fiercer-than-expected Ukrainian resistance.
Sooner or later, Russian quantitative and qualitative military superiority might give Putin his so-desired victory. But then the unconventional war will begin, and Ukrainians have been preparing for that since Russia's invasion and seizure of Crimea in 2014.
US and Western special-operations forces have worked extensively with the Ukrainian military in the years since, setting up commando units, training them, and preparing them to wage a guerrilla campaign against an occupying force.
Now that Putin has invaded Ukraine for the second time in less than a decade, the lessons that US commandos taught their Ukrainian counterparts have deadly relevance.
Unconventional warfare is the bread and butter of the US Army's Special Forces Regiment — the Green Berets — and members of the 10th Special Forces Group, which has Europe as its area of responsibility, have worked with Ukrainian special-operations forces.
Reports also indicate that the US intelligence community has provided special-operations and intelligence training to Ukraine.
Guerrilla warfare
Thus far, Russian forces appear to have tried not to engage civilians, which may be an effort to avoid alienating Ukrainians in keeping with Moscow's attempts to portray the invasion as "liberating" Ukraine.
But there have been hundreds of civilian deaths, according to the Ukrainian government, and a guerrilla war in Ukraine, home to 44 million people, will also be bloody for defenders, insurgents, and bystanders.
When it comes to guerrilla tactics, Ukrainian resistance would target Russian soft spots. A column of T-90 main battle tanks that is supported by mechanized infantry is a hard target, but the supply trucks and depots that support them are softer targets that Ukrainian guerrillas would zero in on to counter Russia's numerical and technological superiority.
"The Russians' logistics chain, which is already in a mess trying to keep their troops supplied, would become a primary target. They are soft-skinned, road-bound, and are staffed by conscripts, not professional warriors," Steve Balestrieri, a journalist and retired Army Special Forces warrant officer, told Insider.
"They won't attack a battalion tactical group head-on. They attack and exploit gaps in the formations. The rear-echelon troops are especially vulnerable," Balestrieri said.
The morale of the Russian occupiers will be another target. A US defense official has said morale is low among Russians in Ukraine now, and footage of the fighting shows that Russian troops are not being welcomed.
Civilians are already openly protesting the Russian invaders, even going as far as standing in front of tanks to stop military movements. Russian soldiers occupying the country will be targeted early and often.
"[Occupied] government buildings, isolated outposts, small groups of Russian soldiers would all be targets. If any high-ranking officers or politicians visit, they would all be likely targets for guerrilla attacks. The Russian battalion tactical groups are ill-prepared for being occupying powers in the cities of Ukraine," Balestrieri added.
Guerrilla forces draw their strength from surprise, not might, and US and Western special operators would have trained Ukrainians to bide their time and strike when an enemy is most vulnerable, a Green Beret assigned to a National Guard Special Forces group told Insider.
"An untrained guerrilla with an anti-tank weapon will just want to shoot at the first tank he sees and scoot to the woods for safety. But a well-trained guerrilla will know to let the first few tanks pass and then strike them either from behind or strike the supply trucks," said the Green Beret, who was not authorized to speak publicly.
Ukraine's borders with four NATO members would also facilitate an insurgency by making it easier to support. Weapons, supplies, and reinforcements would have a relatively easy time entering and exiting the country.
"The guerrilla force will have plenty of external sanctuaries to the west where NATO will provide plenty of support. While the terrain doesn't offer the kind of concealment that we've previously considered, Ukraine is vast — the second-largest country in Europe — and the guerrillas can strike at any place of their choosing," Balestrieri added.
Using improvised explosive devices, guerrillas "would wreak havoc on the Russians trying to cover a country the size of Texas," Balestrieri said.
As the defenders against an invading force, they would also have an advantage in the information domain.
"Controlling the narrative would be a big boost for the Ukrainians," Balestrieri told Insider. "Putin framed this as a war against Nazis and fascists, but he really fears democracy on his border, which could result in regime change" in Russia.
Stavros Atlamazoglou is a defense journalist specializing in special operations, a Hellenic Army veteran (national service with the 575th Marine Battalion and Army HQ), and a Johns Hopkins University graduate.