A Moscow-linked assassination plot forces Stefan Thumann allegedly into hiding. The Donaustahl boss, however, is anything but low-key

Several German companies supply arms technology to Ukraine. When it comes to kamikaze drones, competition is fierce – and it sometimes spills over into social media scraps and media reports that look suspiciously like they were commissioned. The most swashbuckling manager is probably Stefan Thumann, founder and boss of the arms start-up Donaustahl. Among other things, he markets the small quadcopter “Maus”, steered with pilot goggles and to be fitted with grenades, which can be used against armoured as well as “soft” targets.

Thumann has since deleted his often brash postings on Facebook, LinkedIn and X, aimed at “Russia’s henchmen” – though not because of potentially business-damaging behaviour. The “Zeit” newspaper explained the reason two weeks ago: there is a murder plot against the 39-year-old, allegedly directed from Russia, and Thumann has therefore been under police protection since December 2025.

A man named Sergey N. is said to have photographed the entrance to Thumann’s home in Lower Bavaria – which German authorities regard as reconnaissance prior to a possible attack. Analysis of the man’s mobile phones is said to have yielded “indications” of contacts with a Russian intelligence service. The Ukrainian N. later travelled with his family to Spain and was arrested there in March, while a second suspect, the Romanian Alla S., was detained in North Rhine-Westphalia.

Thumann, according to “Zeit”, is a hunter and sport shooter and sold theological specialist literature and surplus Bundeswehr clothing and planned solar parks. He founded Donaustahl in 2019. After the Russian invasion of Ukraine, he converted the production line from sporting accessories to the “Maus”. Such rotor-driven vertical take-off quadrocopters are available in abundance; in Ukraine, tens of thousands are also manufactured by DIY methods. Nevertheless, Thumann managed to draw attention to his “Maus” through his bold statements and, according to his own account, raised €4 million in fresh capital via crowdfunding last year. After that, things went very quiet around Donaustahl.

On German RTL Television and in “Stern” magazine, the manager now speaks out in an “exclusive interview”. He says he is living de facto underground, with no private life, has written his will and signed an organ donor declaration. Thumann now sleeps next to his computer, and when he wakes up he starts working immediately, to avoid having to think about his perilous situation as much as possible. He described the war in Ukraine as his “very personal war” and himself as one of the greatest dangers to the Putin regime in Europe.

Nothing further is currently known about the investigation into the “disposable agents” who are said to have spied on Thumann. The arrest warrant against the two is on suspicion of secret service agent activity – it does not include the allegation of a planned assassination. “I am engaged in a duel with Russian military intelligence for my life!”, Thumann nevertheless claims in the “exclusive interview”. It could be true, or it could not.

Published in German in „nd“.

Image: Before the Ukraine war, Donaustahl sold weapon accessories; here, start-up boss Thumann poses in 2022 with a semi-automatic pistol and extended stock (Stefan Thumann/Facebook).