The destruction wreaked on a Russian battalion as it tried to cross a river in northeastern Ukraine last week is emerging as among the deadliest engagements of the war, with estimates based on publicly available evidence now suggesting that well over 400 Russian soldiers were killed or wounded…

“I’ve been keeping quiet for a long time,” Yuri Podolyaka, a war blogger with 2.1 million followers on Telegram, said in a video posted on Friday, saying that he had avoided criticizing the Russian military until now.

“The last straw that overwhelmed my patience was the events around Bilohorivka, where due to stupidity — I emphasize, because of the stupidity of the Russian command — at least one battalion tactical group was burned, possibly two.”

Mr. Podolyaka ridiculed the Kremlin line that the war is going “according to plan.” He told his viewers in a five-minute video that, in fact, the Russian Army was short of functional unmanned drones, night-vision equipment and other kit “that is catastrophically lacking on the front.”