[UPDATE]: The bridge was destroyed not on January 9, but on February 6, i.e. just 1 day before the attack.
Over 200 Russian military contractors were killed by US airstrikes in Syria on February 7, 2018.
The contractors were members of the so-called Wagner Group private military company (https://en.wikipedia.org/wiki/Wagner_Group). Russian law officially bans mercenary service and private military companies, so in really the Wagner Group is just a unit of the Russian Ministry of Defence in disguise. Many of the Wagner contractors gained military experience in eastern Ukraine before departing to Syria.
Khusham is an oil-rich area in Deir el-Zour province in north eastern Syria, which has been the major source of revenue for ISIS in 2014-2017. In September 2017, the area was liberated by U.S.-backed Syrian Democratic Forces (SDF).
Although Assad is now controlling about 50% of the territory of Syria together with his allies Russia and Iran, he still needs resources to cover his expenses on war and to keep his regime alive.
By some information, Assad proposed a deal to Putin – to keep 25% of all oil resources that Putin helps Assad to return back under his control. US, which wants to remove the tyrant Assad from power in Syria, obviously opposes that.
Russian attack on SDF started at 10 pm on February 7, 2018. Initially, only one battalion tactical group participated in the attack, which included more than 10 tanks and 30 other armored vehicles.
US forces responded to this attack with devastating strikes using high-precision weapons, probably including HIMARS rocket systems. The latter rocket systems destroyed Russian cover artillery batteries, while drones were used to help to guide fire.
After Russian artillery and Russian-Syrian offensive operational groups were destroyed, subsequent strikes destroyed rearguard units, which basically eliminated the second battalion tactical group.
Simultaneously with artillery strikes, electronic warfare system was operating, which completely suppressed radio communication with the offensive groups.
The air space was most probably controlled by two pairs of F-22 Raptors, which monitored possible appearance of Russian aviation in this region.
In 2 hours, 80% of all Russian and Assad forces were destroyed. Then, elimination of the remaining small groups began.
Using Lockheed AC-130 and two pairs of attack helicopters covered by F-22’s, Americans wiped out the area from the remaining groups of enemy.
The total losses of Russia and Assad constituted up to 90% of all military vehicles and 70-80% of manpower. Americans didn’t have any losses. The total duration of the operation was about 6 hours.
Link to the article in Washington Post: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwj0s6nt4q3ZAhXi1IMKHTQiAV8QFggsMAA&url=https%3A%2F%2Fwww.washingtonpost.com%2Fblogs%2Fpost-partisan%2Fwp%2F2018%2F02%2F09%2Fin-syria-russian-bad-faith-turns-fatal%2F&usg=AOvVaw3gnespuqdNluRnWqervVe_
Link to the Wargonzo channel which posted radio communication of Wagner contractors: https://t.me/wargonzo
Russian mercenaries filed a lawsuit to the International Criminal Court (ICC) in The Hague against owners of illegal private armies: