If authentic, the documents — which look like secret US assessments of the war as well as some espionage against allies — offer rare insight into Washington’s view of one of Europe’s deadliest conflicts since World War II.

The Reuters news agency has not been able to independently verify the documents. Some countries, including Russia and Ukraine, have questioned their veracity, while US officials have said some of the files appeared to have been altered.

One February 23, 2023 assessment, titled, “Battle for the Donbas Region Likely Heading for a Stalemate Throughout 2023”, said Russia is unlikely to be able to take that part of east Ukraine.

“Russia’s grinding campaign of attrition in the Donbas region is likely heading toward a stalemate, thwarting Moscow’s goal to capture the entire region in 2023,” read the assessment above a classified map of Russian positions.

“These tactics have diminished Russian forces and munition stockpiles to a level that, barring an unforeseen recovery, can exhaust Russian units and frustrate Moscow’s war aims, resulting in a protracted war beyond 2023.”

Russia’s defence ministry did not respond to a request for comment. Moscow has said it does not know if the documents are real and that they may be an attempt to sow discord.

According to an assessment found in the leaks, seemingly collated by the US Defence Intelligence Agency, Russia has suffered 189,500 to 223,000 total casualties, including 35,500 to 43,000 killed in action and 154,000 to 180,000 wounded.

Ukraine has suffered 124,500 to 131,000 total casualties, including 15,500 to 17,500 killed in action and 109,000 to 113,500 wounded in action, according to the document titled, “Russia/Ukraine – Assessed Combat Sustainability and Attrition”.

The figures are approximately 10 times larger than any public casualty figure published by either Moscow or Kyiv.

Neither side gives timely data on military losses.

US wary of provoking China

One US document posted on Russian Telegram channels had the casualty figures crudely altered to reduce Russian casualties and increase Ukrainian casualties. Reuters has seen two versions of the same document with one clearly altered.

“RUS continues to fall behind stated goals for the replenishment of equipment and personnel to support operations in Ukraine,” the purported Defence Intelligence Agency assessment read, stressing that there were significant gaps in information.

The document on casualties was embossed with emblems of the US Joint Chiefs of Staff and the Defence Intelligence Agency.

Both Russia and Ukraine were assessed to have “moderate” combat sustainability, which meant that both are likely to be able to continue to fight for some time.

The documents indicated that while Russia had overall numerical superiority in some areas, Ukraine had more tanks and armoured personnel carriers (APCs) in theatre than Russia.

Russia, according to the Defence Intelligence Agency analysis in the document leak, has lost 2,048 tanks and 3,900 APCs while Ukraine has lost 468 tanks and 1,020 APCs. Ukraine has 802 tanks and 3,498 APCs fielded, while Russia has 419 tanks and 2,928 APCs in theatre.

Russia had superiority in fighters and air defences, according to the document on casualties. Reuters was unable to verify the figures, which are at odds with Russian tallies of its destruction of Ukrainian equipment.

The leaked documents also suggested concerns in Washington about Ukrainian attacks deep into Russia — and even potentially on Moscow — due to the impact such attacks could have on China’s position.

“China would respond more strongly and most likely increase the scale and scope of material it is willing to provide Russia if Ukrainian strikes hit a location of high strategic value or appeared to target senior Russian leaders,” said what appeared to be a collation of US intelligence assessments.

Reuters has reviewed more than 50 of the documents, labelled “Secret” and “Top Secret”, that first appeared on social media sites in March. They purportedly reveal details of Ukrainian military vulnerabilities and information about allies including Israel, South Korea and Turkey.