On a spring day in 2013, two soldiers from Australia's elite Special Air Service Regiment had their photograph taken in Uruzgan Province, central Afghanistan. Nine years later, this photo has resurfaced in a scheme to recruit mercenaries for Russia's invasion of Ukraine — all without the soldiers' knowledge. The photo has been used on billboards that belong to the mysterious Wagner Group, an organisation known in the West as "Putin's private army" and which did not officially exist until this year. Former US military photographer Gagan Dhiman was embedded with the Australian soldiers at the Tarin Kowt military base when…