The Wagner group of mercenaries is currently training Belarus’ soldiers with thousands of their mercenaries.

In order to guard against Wagner fighter incursions, Poland is sending an additional 10,000 troops to the Belarusian border.

A BBC investigation has revealed that several prisoners recruited by Wagner to fight in Ukraine have been charged with serious crimes since returning home.

Yevgeny Prigozhin, Wagner’s leader, says the group was founded in 2014.

As a wealthy businessman with a criminal record, Prigozhin provides catering to the Kremlin.

Wagner is believed to have helped Russia annex Crimea in 2014, when he began supporting pro-Russian separatist forces in eastern Ukraine.

In Africa and the Middle East, Wagner forces are also active.

It is believed that the group’s name comes from the radio call sign of its first field commander, Dmitry Utkin.

Wagner had an estimated 5,000 fighters before the Ukrainian war, most of whom were veterans of Russia’s elite regiments and special forces.

Prigozhin, however, said last June that its numbers had increased to 25,000 since the beginning of the Ukraine war.

Mercenary forces are technically illegal in Russia, but Wagner registered as a “private military company” in 2022.

During the Russian invasion of eastern Ukraine, Wagner played a major role in capturing Bakhmut.

According to Ukrainian troops, its fighters were sent into attacks in large numbers over open ground, and many of them were killed.

Before Russia invaded, Wagner is believed to have carried out “false flag” attacks in Ukraine to give the Kremlin a pretext for invasion. Attacks that one side commits while blaming the other side for them.

According to Prigozhin, Wagner has recruited 49,000 prisoners from Russian prisons.

For serving six months in Ukraine, they received pardons and 100,000 roubles ($1000, £800).

According to Prigozhin, 32,000 prisoners have returned, but independent researchers suggest that the number may be as low as 20,000.

Since returning to Russia, 20 former prisoners who fought for Wagner in Ukraine have committed serious crimes, including rape and murder.

Along with Prigozhin, Wagner fighters had the option of joining the regular army of Russia or going to Belarus.