Lev Stupnikov, a 26-year-old Russian signals lieutenant, spent seven months secretly feeding his army's battle plans to Ukrainian military intelligence — intelligence Ukraine used to kill more than 300 Russian soldiers, including his own brigade commander. The Wall Street Journal's investigation, published October 16, 2026, reads like a spy novel: a disillusioned young officer, a WhatsApp message to a Ukrainian handler, and a midnight walk across no-man's-land guided by a drone.
How a 26-year-old lieutenant turned on his own army
Stupnikov was the chief signals officer of a battalion in Russia's 36th Separate Guards Motorized Rifle Brigade, stationed at the front-line village of Mykilske in Donbas and tasked with capturing the stronghold city of Vuhledar. A graduate of the Budyonny Military Academy of the Signal Corps in St. Petersburg, he was commissioned as a lieutenant in April 2022 — and was already disillusioned, having been appalled by Russia's full-scale invasion and by bribe demands at the academy years earlier.
In February 2024, three months into his front-line service, his mother Tatiana Yantsen wrote to Dmytro Karpenko, a computer programmer working closely with Ukrainian military intelligence who ran a YouTube channel posting interviews with Russian POWs and had announced payments of 250,000 rubles (about $2,700) to Russian servicemen supplying useful information. Stupnikov then messaged Karpenko on WhatsApp: "I'm ready to work with you, and to give myself up," attaching his name, rank, location, battalion and brigade. His single condition: no money was to change hands.
The leaks that killed more than 300 soldiers
From his signals post, Stupnikov passed Ukraine exact coordinates of troop gatherings, radio frequencies, troop locations and detailed battle planning — who was being sent where, and when tanks would advance. He also carried out active sabotage: disabling cameras monitoring Ukrainian territory and cranking the voltage on a drone-controller battery pack so it overheated and failed mid-mission.
The first strike came in February 2024. Stupnikov flagged a training field near Vuhledar where 120 to 150 men were drilling; a Ukrainian missile barrage killed 68 and wounded 60, including 10 officers — among them Col. Gusein Musayev, commander of the 36th Brigade. It was one of the highest single-strike tolls of the war. His text to his handler afterward: "There's just meat."
More followed. In March 2024, officers were killed at a large brigade gathering he had flagged. In May 2024, 20 were killed including a captain in a strike on a former hotel basement housing two assault units, and another strike hit a brigade command post during a high-level meeting. In total, Ukraine used his intelligence to kill more than 300 Russian soldiers, according to interviews with his handlers, video footage, text exchanges and official Russian reports. His brigade, the Journal reports, "was losing soldiers at a rate that stood out — even in a Russian army that was hemorrhaging men." His commander suspected a mole: "Nothing we're doing is working out. I have a feeling there's a Stierlitz in our ranks" — a reference to the fictional Soviet sleeper agent.
A midnight walk across no-man's-land
By late May 2024, Stupnikov was nearly caught: he accidentally sent Karpenko a screenshot of his own basement location and narrowly survived the resulting strike. On the night of July 6, 2024, he walked out of Mykilske carrying his radio and smartphone, crossed no-man's-land on foot for about 40 minutes guided by a Ukrainian drone, and gave the password "Peanut shop" to troops of Ukraine's 72nd Brigade, who took him in blindfolded. He handed over a smartphone with passcodes to communication channels that gave Ukrainians live feeds from a dozen Russian drones and surveillance cameras for months afterward.
Now he fights against his old brigade
Stupnikov has since joined the Russian Volunteer Corps, a Ukrainian army unit of ethnic Russians opposed to Vladimir Putin led by Denis Kapustin — and now fights against the brigade he left behind, maintaining communications equipment near the front. Russia has opened two criminal cases against him, for treason and desertion, and placed him on the federal wanted list. His mother Tatiana and his teenage sister Alisa crossed on foot from Moldova into Ukraine in February 2025 and were reunited with him in Kyiv. His wife Liza stayed in Russia and later told Russian state media his act was treason: "He betrayed me too."
His story has already inspired copycats: Karpenko's informant pipeline is now a 24/7 operation, with longtime sources earning $4,000 a month. But the Journal notes a cautionary parallel — defector pilot Maksim Kuzminov, who flew an Mi-8 helicopter to Ukraine for a $500,000 reward, was assassinated in Spain six months later, in February 2024. Stupnikov, asked if he had betrayed his oath, answered: "Did I betray my oath? … But Putin destroyed all three."
Takeaway: Seven months of leaks from a single disillusioned lieutenant killed more than 300 soldiers and decapitated a Russian brigade's command — a reminder that in modern warfare, the most dangerous weapon can be a man with a radio who has stopped believing.
Watch: Dmytro Karpenko's original two-hour video interview with Lev Stupnikov — the defector recounts in his own words how he leaked his brigade's coordinates and battle plans to Ukrainian intelligence for seven months, the first-hand source material behind the WSJ investigation.
Music in this post's reel: Kevin MacLeod - Darkening Developments (incompetech.com), licensed under CC BY 3.0