Russia has suffered more casualties in the Ukraine war than all other conflicts combined since World War II: Pentagon

U.S. officials say Russia has suffered about 600,000 casualties in its war with Ukraine – more than casualties in every conflict since World War II combined.

This September was Russia's deadliest month of the entire war, a senior U.S. defense official said in a phone call with reporters on Wednesday.

“Russian losses, again both dead and wounded, in the first year of the war already exceeded the total of all Soviet losses in every conflict since World War II combined,” the official said.

However, the heavy losses are not a “definitive measure” of Ukraine’s success, the official warned. Ukraine also suffered numerous casualties, although the USA did not disclose how many there were.

Ukrainian President Volodymyr Zelensky said in February that about 31,000 soldiers had been killed.

Britain's Defense Ministry put Russia's daily casualties at 1,271 in September and said about 648,000 Russians had been killed or injured in the war.

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Ukrainian forces inflicted around 600,000 casualties on Russian forces. (Reuters/Lisi Niesner)

“It's kind of a Russian style of war where they continue to invest heavily in the problem, and I think we're going to continue to see high casualties,” the U.S. military official said.

South Korea warned earlier this week that North Korea would send its troops to fight alongside the Russians.

Russia also lost two-thirds of its pre-war tank inventory to Ukraine, along with 32 medium to large naval vessels.

Russian President Vladimir Putin is trying to “avoid mass mobilization because it would impact the Russian population,” the official said.

“At that point, he was able to significantly increase the salaries of these volunteer soldiers, and he was able to continue to raise these forces without conducting a major mobilization.”

“And I think we're just watching very closely to see how long he can actually maintain that posture, and I think it's important for all of us to watch very closely,” the official added.

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The Ukrainian military said it attacked a base in Russia's southern Krasnodar region on Wednesday that was home to nearly 400 attack drones.

Russia has made some progress in the Donetsk region, seizing the town of Vuhledar earlier this month and advancing toward Povrosk, a key railway hub and supply station for Ukraine.

A woman stands in the backyard of her house, which was destroyed by a Russian airstrike during Russia's attack on Ukraine, on Thursday in Zaporizhzhia, Ukraine. (Reuters/Stringer)

This September was Russia's deadliest month of the entire war, a senior U.S. defense official said in a phone call with reporters on Wednesday. (Reuters/Viacheslav Ratynskyi/File Photo)

The U.S. official said the Russian strategy around Vuhledar and Povrosk had produced “significant losses” for small gains.

There is also heavy fighting in the Russian region of Kursk, which Ukraine invaded in August. Ukraine had hoped to withdraw Russian troops from the front to defend Kursk. Russia has since retaken part of the region, although the military official said Ukrainian troops could hold the Kursk region for months or longer.

Meanwhile, the US continues to invest billions in Ukraine's defense. Last month, President Biden announced an $8 billion package for Kyiv to provide it with military equipment by January. It is the last of the $61 billion that Congress approved for Ukraine in April.

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Despite Zelensky's demands, Biden has resisted authorizing Ukraine's use of U.S.-provided long-range missiles, known as ATACMs, to strike inside Russia and destroy its weapons stockpile, fearing escalation.

Many U.S. lawmakers have supported Zelensky's request, but the U.S. official said the Biden administration is not considering reversing its policies. He said many of the weapons Ukraine wants to destroy, such as Russia's deadly glide bombs, have been removed from the range of ATACMs.