Following the circulation of a video showing the assault, law enforcement opened criminal proceedings under Part 2 of Article 406 of Ukraine's Criminal Code, which covers violations of statutory rules governing relations between military personnel.
The suspect was detained in Kropyvnytskyi, transferred to Dnipro, and handed over to investigators from the State Bureau of Investigation.
Prosecutors said they plan to formally charge him and file a motion for pre-trial detention.
According to investigators, the incident occurred on May 1 at approximately 4 p.m. at the unit's temporary base in Dnipro. During a formation, a drone operator publicly humiliated another soldier and physically assaulted him, delivering multiple blows.
The suspect then allegedly left his post without authorization. The victim was hospitalized at a Dnipropetrovsk Oblast hospital with bodily injuries and received medical treatment.
A video showing one soldier beating another in front of a military formation circulated online earlier this week.
Initial speculation suggested the attacker was 155th Brigade commander Stanislav Luchanov, who previously served as chief of staff of the 425th Separate Assault Regiment "Skelia." Both the Ukrainian Ground Forces and the brigade denied his involvement.
The Military Law Enforcement Service of the Armed Forces of Ukraine subsequently said the assault was carried out by a soldier serving as a drone operator.
The 21st Corps, to which the 155th Brigade belongs, said the soldier who carried out the beating is not a member of that unit.
Commander-in-Chief of the Armed Forces of Ukraine Oleksandr Syrskyi ordered an internal inquiry into the incident, tasking the Eastern Territorial Directorate of the Military Law Enforcement Service with conducting it. Materials gathered during the inquiry will be forwarded to law enforcement upon its conclusion.