Russia has now admitted to losing two of the officers in a single day; the death also includes one person who had been sent to replace a colonel who had died earlier in the war.
Lieutenant Colonel Denis Sukhanov, aged 41, has been reported dead as he was "defending civilians" the exact location and the date of his death are unknown.
Kozlov, the second commander of the 12th separate Guards Engineering, has been reported dead in the conflict. He was being sent to Ukraine to replace Colonel Sergei Porokhnya, who had died earlier. Meanwhile, Colonel Denis Kozlov has been dead; he died during a botched mission to cross the Donets River last week.
Hence the death of the Russian Army's soldiers is considered a huge setback for Russia.