For months, important facilities across Russia have been hit by mysterious fires and explosions.
The incidents have little obvious explanation but seem to have affected a narrow set of targets.
Some may be the work of Russians opposed to Putin; others show signs of military special operations.
The war in Ukraine isn't going well for Russia's military. In a matter of a days this month, Ukrainian forces managed to liberate more territory than the Russian military captured and held over six months of war.
But the Russian military's struggles aren't limited to inside Ukrainian borders.
For months now, sensitive sites and important facilities throughout Russia have been hit by mysterious fires and explosions, hinting at a sabotage campaign that is the hallmark of special-operations forces.
Mystery fires and explosions
In May, as the Russian military was preparing to launch a renewed offensive in Ukraine's Donbas region, military outposts, recruitment centers, and defense industrial complexes across Russia started suffering mysterious explosions or fires.
In all, there have been dozens of incidents at facilities throughout Russia with little obvious explanation.
The targets include oil refineries, ammunition production and storage facilities, aerospace and defense companies, and communications infrastructure. The attacks appear to be part of an effort to undermine and degrade the Russian military's offensive capabilities.
The perpetrators may not all be working together.
In May, for example, Russian authorities caught two Russian teenagers throwing Molotov cocktails at a military commissariat - essentially a recruitment station. Dozens of commissariats have been attacked in Russia this year, suggesting that some Russians, especially those likely to be drafted into the military, are opposed to the war.
But the attacks seem to focus on a narrow set of targets, and the incidents have largely aligned with what military special-operations units would be tasked with as part of an unconventional-warfare campaign.
A guerrilla campaign inside Russia
Unconventional warfare is a skill set that the US special-operations community excels at and with which it has decades of experience conducting and training others to conduct.
Since the US military isn't directly involved in the fighting in Ukraine, the source of the attacks is likely Ukrainian commandos or Russian dissidents - or possibly a combination of both.
Such a guerrilla campaign could gain steam if Russia continues to fail in Ukraine, and it could take many forms, a Green Beret assigned to a National Guard Special Forces unit told Insider.
"At the start, it may look like a disruption campaign, like the one we saw in Belarus with the trains. Targeting and attacking the supply lines and other soft targets is always on the list," said the Green Beret, who was not authorized to speak to the media and spoke on the condition of anonymity.
"Next on the list would be harder targets, such as military convoys, bases, or even attacks on command-and-control facilities and headquarters," the Green Beret added.
After 2014, when Russia attacked Ukraine by seizing Crimea and invading the Donbas, US Special Operations Command ramped up its training, assistance, and advising for Ukrainian forces.
Green Berets from the 10th Special Forces Group, which has Europe as its area of operations, have been pivotal in bringing up the Ukrainian special-operations community up to speed.
The effectiveness of that American instruction is now visible to the world in the Ukrainian military's operations. Some of those operations appear to have struck inside Russian territory, including an attack on a fuel dump in the city of Belgorod in April that Russia blamed on Ukrainian helicopters and missile strikes on Russian bases in Crimea in August.
"But eventually a guerrilla campaign would have to mature and adapt on the expected security measures that the Russian military and security services will take to respond to the attacks," the Green Beret told Insider.
While many Russians have expressed opposition to or dismay about President Vladimir Putin's war in Ukraine, the most difficult part of such a campaign for Ukraine may be winning over the Russian public, the Green Beret said.
"A lot of Russians are fiercely patriotic, and Putin has spun the war quite smartly to appeal to the ordinary Russian," and an unconventional-warfare campaign "is very hard to pull off" against a hostile population, the Green Beret added.
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. He is currently working toward a master's degree in strategy and cybersecurity at the Johns Hopkins School of Advanced International Studies.