I was initially very skeptical (oh no! I'm turning into JamesR!) that the leaked reports were real. But the reaction of the US government suggests that they were. Or at least that they want somebody (the Russians?) to think they are real secret information.
seem to suggest that there have been a total in excess of 310,000 so far in the war - killed and injured. c.190k+ on the Russian side, c.120k on the Ukrainian. The report says, however, that "the Pentagon says it has '
low confidence' in the figures, due to gaps in information, operational security and deliberate attempts, probably by both sides, to mislead."
I expect that deep within the US and allied governments, somebody has a good idea what actual casualty figures are.
The President of the European Commission Ursula Van der Leyden famously blurted in November 2022 that "more than 100,000 Ukrainian military officers have been killed so far." (She probably meant military personnel in total, not just officers.)
https://twitter.com/thenobodyz/status/1597895930165878786
Then in January 2023 the Norwegian Army Chief of Staff said that Russia has suffered over 180,000 military casualties (both killed and wounded) and the Ukrainians "over 100,000".
Ukraine keeps their casualty numbers a closely guarded secret, tells outsiders not to believe any numbers that don't come from their government, and say that they will release the figures when the time is right.
In terms of deaths, the leaks (if genuine) suggest 16-17.5k on the Ukrainian side, although on a pro-Russian site those numbers appear to have been assigned to Russian fatalities, with the numbers reversed for Ukrainian (so 61-71.5k).
Somebody clearly seems to have altered the figures. The question is whose hands these documents have passed through, what else was changed, and how good the information was in the first place. I'm hugely doubtful.
The more interesting details in the documents seem to be revelations about Ukrainian ammunition shortages. They make it sound like Ukraine is very low on surface to air missiles and the GMLRS precision-guided rockets fired by HIMARS.
For their part, the Russians are very skeptical about the whole thing. They believe that the leaks were made intentionally and are low-balling the Ukrainian supply situation in hopes of enticing the Russians into making mistakes. A psychological-operation in other words. And if so, it seems rather amateurish in my opinion. (A Minecraft site on Discord?)
If these were real briefing papers for the Chairman of the Joint Chiefs of Staff, it's even worse, since by all accounts the information they contain seems to consist of little that couldn't have been gleaned from open sources. If that's the best that vaunted US intelligence can do, it's just sad.