Short answers, pulled from the story.
The Wagner Group first appeared in Syria in late October 2015, when a rebel mortar attack in Latakia province killed between three and nine of its contractors. Their presence was first reported almost a month after the start of Russia's official military intervention in the civil war. Sources within the FSB and the Russian Defense Ministry confirmed to Russian media that Wagner was supervised by the GRU, Russian military intelligence.
By July 2017, the Kremlin had established a policy giving companies that seized oil and gas wells or mines from ISIL production rights at those same sites. One company employing Wagner was to receive 25 percent of the proceeds from any oil and gas fields its contractors captured and secured. The total cost of Wagner's operations to Russia had reached 170 million dollars by August 2016.
Wagner PMCs served as frontline advisors, fire and movement coordinators, and forward air controllers in both the 2016 and 2017 Palmyra offensives. One contractor described their role as "cannon fodder," with the PMCs doing most of the fighting. The first offensive in 2016 cost an estimated 32 contractors killed and around 80 wounded; the second in 2017 saw between 40 and 60 killed and between 80 and 180 wounded.
Russian independent media identified several perpetrators, including Stanislav Yevgenyevich Dychko, a confirmed Wagner operative and former Russian Interior Ministry employee, and a former soldier named Ruslan from Bryansk. No criminal cases were opened after the Novaya Gazeta submitted investigation material to the Russian Prosecutor General. In December 2021, the European Union sanctioned Wagner's commander Dmitry Utkin, citing a former member's testimony that Utkin "personally ordered the torturing to death of the deserter as well as the filming of the act."
At approximately 10 pm on the 7th of February 2018, pro-government forces including Wagner contractors clashed with the Kurdish-led SDF near Khasham in the Deir ez-Zor Governorate. U.S. aircraft struck the government side, killing between 45 and 100 fighters. Casualty estimates for Russian PMCs specifically ranged from 13, reported by Novaya Gazeta, to claims of over 200 on Russian social media, with Wagner leader Andrei Troshev quoted on the 19th of February as saying 14 "volunteers" died and Russia officially confirming five.
The Syrian Observatory for Human Rights reported on the 15th of March 2023 that 266 Russian PMCs had been killed in Syria over the course of the civil war. The count covered nearly eight years of operations across multiple fronts, including Palmyra, Deir ez-Zor, Hama, and the Syrian desert.