Lev Stupnikov leaked Russian troop positions to Ukraine before defecting in 2024. An investigation examines his role and the reported tolls.
UKRAINE — A Russian lieutenant secretly supplied Ukrainian intelligence with troop positions and battle plans in 2024, then crossed the front line, according to a new investigation published on Friday
A Russian army communications officer spent months providing sensitive battlefield intelligence to Ukraine before abandoning his military unit and joining Russian nationals fighting against Moscow, according to an investigation published by The Wall Street Journal on October 16, 2026.
The officer, Lev Stupnikov, now 26, allegedly helped Ukrainian forces identify Russian troop concentrations, monitor military communications and launch strikes that killed more than 300 Russian personnel.
The reported death toll, based on Ukrainian assessments and evidence examined by the newspaper, has not been independently established through a complete public casualty record.
His case illustrates how a single insider with access to operational communications can create a serious security vulnerability within a military formation. It also offers a rare account of the personal, political and operational circumstances surrounding a Russian officer's decision to cooperate with Ukraine during the war.
Inside the Russian Brigade Near Vuhledar
Stupnikov served as a communications officer with Russia's 36th Motor Rifle Brigade, a formation operating around Vuhledar in Ukraine's eastern Donetsk region.
His responsibilities gave him access to information extending beyond the routine duties of a frontline soldier. Military communications personnel can encounter radio frequencies, battlefield reports, surveillance feeds and operational messages connecting commanders with subordinate units.
For Stupnikov, that access reportedly provided a detailed picture of Russian positions and planned operations.
He had graduated from a military communications academy in St. Petersburg and entered service during a period of intense pressure on Russia's armed forces following the full-scale invasion of Ukraine in February 2022.
According to the investigation, he was increasingly disillusioned with the war and the conditions inside the Russian military.
By early 2024, his dissatisfaction had developed into active cooperation with the country his military had invaded.
That decision placed him in an unusual and exceptionally dangerous position. He continued performing his official duties while covertly helping Ukrainian forces obtain information about the personnel and equipment around him.
The Intelligence Contact That Changed His Role
Stupnikov's cooperation with Ukraine began in February 2024, with assistance from his mother, Tatiana Yantsen, who opposed the Russian invasion.
She helped facilitate contact with Dmytro Karpenko, a Ukrainian intermediary who had become known for interviewing Russian prisoners of war and communicating with people willing to assist Ukraine.
The lieutenant reportedly identified himself, his rank and his military assignment before supplying information about his unit.
The arrangement differed from a conventional paid intelligence relationship. Although Karpenko had previously advertised financial rewards for actionable military information, Stupnikov reportedly declined payment.
That distinction matters when evaluating the case. The investigation portrays his actions primarily as a political and moral rejection of the war rather than an operation driven by financial gain.
It does not, however, establish that ideological opposition alone explains every decision he made.
His cooperation soon moved beyond communications with a Ukrainian intermediary to information that could directly influence battlefield targeting.
A February 2024 Missile Strike
One of the most consequential incidents occurred near Vuhledar in February 2024.
Russian troops had assembled for military training ahead of a planned offensive. Officers and other personnel were present at an exposed training area when Stupnikov reportedly confirmed their concentration to his Ukrainian contact.
He had already passed along the location.
According to the Wall Street Journal investigation, Stupnikov subsequently moved away from the assembled personnel before Ukrainian forces struck the site.
The reported casualties were 68 Russian personnel killed and approximately 60 wounded. Among those said to have died were 10 officers, including Colonel Gusein Musayev, identified as the brigade's commander.
These figures describe the reported outcome of that particular strike, not the total number of casualties linked to Stupnikov's intelligence activities.
The incident demonstrated a critical distinction between identifying a military location and knowing when valuable targets are actually present.
Satellite imagery, drones and other surveillance systems can reveal military infrastructure and troop movements. An insider, however, may provide immediate confirmation about personnel, command presence and the timing of an activity.
That information can make previously collected intelligence considerably more actionable.
The reported operation was therefore significant not merely because Stupnikov transmitted coordinates, but because he allegedly supplied information about the activity taking place at those coordinates.
Repeated Intelligence Leaks and Equipment Sabotage
The February strike was not described as an isolated incident.
Over subsequent months, Stupnikov allegedly passed along radio frequencies, operational plans, movements of Russian formations and information about military positions.
In May 2024, another strike reportedly hit a building sheltering Russian assault units. The Wall Street Journal account attributed the operation partly to information provided by the lieutenant and reported 20 fatalities, including an officer.
Stupnikov was also accused of interfering directly with Russian equipment.
The reported incidents included disabling surveillance cameras and damaging a drone control system, reducing the effectiveness of equipment used by his own formation.
Taken together, those actions represent two different forms of internal military compromise.
The first involved the disclosure of information that Ukrainian forces could use to understand Russian operations. The second involved physical interference with equipment supporting those operations.
Their combined importance lies in the relationship between information and military effectiveness. A compromised communications network can reveal what a unit intends to do, while damaged surveillance systems can restrict its ability to detect threats.
The investigation connects Stupnikov with strikes that reportedly killed more than 300 Russian troops.
That estimate should be interpreted cautiously. It reflects a reported attribution of casualties to intelligence-supported operations rather than an independently audited count of deaths caused exclusively by one individual.
Russian reporting from 2025 had already described allegations against Stupnikov and referenced a lower estimate of more than 200 possible fatalities. The differing figures demonstrate why precise casualty attribution remains an important unresolved question.
Why His Military Position Was So Sensitive
The vulnerability highlighted by this case was not limited to the physical location of Russian troops.
Modern military operations depend on interconnected systems for reconnaissance, communications, command decisions and the movement of personnel.
An officer responsible for communications may therefore gain visibility across functions that would otherwise be separated.
That creates an insider-risk problem: a person with legitimate technical access can misuse information without necessarily breaching an external perimeter or stealing equipment.
Stupnikov's alleged activities show how such access can become especially consequential in an environment where battlefield information rapidly influences artillery and missile attacks.
The case also reveals the limitations of treating operational security solely as a technology problem.
Secure devices and communications procedures cannot eliminate every threat when an authorized user deliberately reveals protected information.
At the same time, the available public reporting does not establish how extensively Russian commanders detected suspicious activity or which specific security measures failed before his departure.
Those details would be necessary for a complete technical assessment of the breaches.
The July Escape Across the Front Line
As Russian troops suffered repeated strikes, suspicions reportedly grew that sensitive information was reaching Ukrainian forces from inside the brigade.
Stupnikov eventually concluded that remaining in his position was becoming increasingly dangerous.
On the night of July 6, 2024, he crossed from Russian-held territory toward Ukrainian military positions near the Vuhledar sector.
The journey required him to move through dangerous ground between opposing forces, where mines, destroyed equipment and the possibility of being mistaken for an enemy combatant made identification critical.
According to the investigation, Ukrainian personnel had arranged his approach and monitored his movement using a drone.
After reaching Ukrainian positions, Stupnikov identified himself using a prearranged phrase.
His arrival ended months of covert cooperation from within the Russian military.
He reportedly surrendered a smartphone containing access credentials that enabled Ukrainian forces to continue viewing some Russian drone and surveillance feeds.
That detail is significant because it suggests the intelligence value of his cooperation did not necessarily end when he physically left his unit.
For a period after his departure, Ukrainian personnel reportedly retained access to information originating from Russian surveillance equipment.
From Russian Officer to Russian Volunteer Corps Member
Following his escape, Stupnikov met Denis Kapustin, a commander of the Russian Volunteer Corps, an armed formation of Russian nationals fighting on Ukraine's side against Moscow.
He subsequently joined the organization in a communications-related role.
The move represented a further change in his position. Rather than simply abandoning Russian military service or seeking refuge outside Russia, he became associated with an armed group actively opposing the Russian government.
The Russian Volunteer Corps is politically controversial, including because of the far-right background and extremist associations of figures connected with its leadership.
That context is important when assessing Stupnikov's subsequent affiliation. His rejection of Russia's invasion should not be treated as an automatic endorsement of every political position or action associated with the organization he joined.
The personal consequences of the defection were also substantial.
His wife remained in Russia and publicly rejected his decision, according to Russian media accounts.
His mother and younger sister subsequently left Russia and reached Ukraine in February 2025.
Russian authorities pursued the former officer, and Russian reporting in September 2025 stated that he had been placed on a federal wanted list.
Those developments underline how the consequences of a military defection can extend beyond the individual to family relationships, legal exposure and personal security.
What the Case Reveals About Wartime Intelligence
Stupnikov's story became widely known after accounts of his cooperation with Ukraine emerged publicly in 2025. The October 2026 investigation added a more detailed reconstruction of his activities, including the reported strikes, his escape and the role played by individuals who helped him contact Ukrainian intelligence.
It also raises questions about how armies identify insider threats while maintaining the communications access needed to operate effectively.
The broader strategic lesson is not that one individual determined the outcome of a major military campaign. The available reporting does not support such a conclusion.
Rather, the case demonstrates how a relatively junior officer with access to operational systems can allegedly affect multiple military activities over several months.
The reported casualty toll is substantial, but the true extent of Stupnikov's contribution remains dependent on the quality of the underlying military evidence and the accuracy of the assessments provided to journalists.
The case highlights another dimension of the Russia-Ukraine war: the conflict is fought not only through attacks on territory and military equipment, but also through efforts to obtain information from individuals within opposing forces.
For military institutions, the episode presents a stark example of the consequences of compromised operational trust.
For Stupnikov, the decision led from service in a Russian combat formation to a dangerous frontline crossing and ultimately to a new role among Russians fighting against Moscow.
More than two years after his reported escape, the central questions extend beyond his personal story to the security failures, competing loyalties and uncertain casualty assessments that continue to shape the intelligence dimension of the war.
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