Russia is branding foreign mercenaries serving in its army with serial numbers to strengthen control and depersonalize them, according to the Ukraine’s Defence Intelligence
Instead of standard metal military identification tags, Russia uses a system of sequential “inventory numbers” for foreign mercenaries, marking them on their equipment or skin. The markings are applied with long-lasting dyes, such as henna or jagua, meaning they remain visible for weeks and cannot be washed off with soap and water. If a mark fades and becomes difficult to see, it is renewed.
There have been documented cases of Russian police stopping foreigners, including students and migrant workers, and checking them for such numbers. According to Defence Intelligence, this is how Russian security forces search for deserters.

"The system resembles practices used in Nazi concentration camps, where prisoners were assigned numbers in an effort to erase their identity, name and legal status. In effect, the Russian army is turning foreign mercenaries into commodities — numbered assault units," Defence Intelligence said.

The rudimentary marking system allows Russia to leave the bodies of killed foreigners on the battlefield as “unknown,” list them as “missing,” and avoid paying financial compensation to their families in Africa and Asia, while concealing the true scale of its losses.
According to Defence Intelligence, "the use of totalitarian methods to deprive individuals of their names and identities once again demonstrates Russia’s systematic disregard for international humanitarian law."

The intelligence obtained is being shared with foreign partners and law enforcement agencies for inclusion in materials for future international tribunals against Russia’s military and political leadership.