The UK intelligence said that Russia's decision to appoint a new commander shows how poor its performance has been so far.
The UK's Ministry of Defence said in an intelligence briefing on Wednesday that the appointment of Alexander Dvornikov as commander of the war in Ukraine was an attempt to centralize command and control.
Russia's invasion has been hampered by an inability to cohere and coordinate military activity.
The nickname "The Butcher of Syria" was given to Dvornikov, the first commander of the Russian armed forces in Syria, because of the brutal nature of his campaigning there.
The UK Ministry of Defence said that Dvornikov has been in charge of Russia's Southern Military District bordering Ukraine.
It said that the Ukrainian opposition was a factor in the appointment of Dvornikov.
The selection of Dvornikov shows how determined Ukrainian resistance has forced Russia to rethink its operations.
Russia is shifting its focus to the eastern part of the country as its efforts stall across Ukraine, according to the UK briefing.
Russia has lost many senior commanders. Insider reported earlier in April that as many as 18 generals and other senior military figures have been killed in fighting.