As Russia's war on Ukraine approaches its one-year anniversary, Moscow is increasingly suspected of manipulating its official death toll, diminishing its own losses and exaggerating Ukraine's.

Russia's defense minister said last September that 5,937 Russian troops had been killed in the war. In November, U.S. officials estimated that Moscow's casualties were "well over 100,000 Russian soldiers killed and wounded." At the time, American officials estimated that Ukraine's armed forces "probably" suffered a similar number and that as many as 40,000 Ukrainian civilians had been killed.

VOA Interview: What to Know About Russia's Manipulated War Statistics

Especially high in Russia's numbers: casualties among international volunteers fighting for Ukraine.

VOA Interview: What to Know About Russia's Manipulated War Statistics

Ukraine says more than 20,000 foreign volunteers from 52 countries have answered President Volodymyr Zelenskyy's call to help fight Russian forces. Most foreigners fighting in Ukraine are doing so for ideological reasons, though Russia routinely brands them "mercenaries" — a designation that excludes them from the protections guaranteed under the 1949 Geneva Conventions.

VOA Interview: What to Know About Russia's Manipulated War Statistics

Chuck Pfarrer is a writer and former U.S. Navy SEAL who is closely monitoring the situation in Ukraine and maintains contact with American and other foreign volunteers on the ground. He also has covered the conflict for the Kyiv Post.

Pfarrer is the author of "SEAL Target Geronimo: The Inside Story of the Mission to Kill Osama Bin Laden," a New York Times bestseller, which disputed parts of the White House's description of the mission and was called a "fabrication" by a spokesperson for U.S. special operations command. Pfarrer has defended his reporting and said the government was covering up unflattering details.

Pfarrer told VOA on January 3 that Russia's manipulation of statistics is part of a Kremlin disinformation narrative to justify military aggression in Ukraine.

"Putin desperately wants Russian citizens to think that Russia is 'fighting NATO' in Ukraine," Pfarrer said. "The more 'international' deaths Russia can claim, the easier it will be for him to sell this fantasy."

This interview has been edited for length and clarity.

Since the beginning of its full-fledged invasion last February, the Russian Defense Ministry has announced daily heavy losses delivered to Ukrainian troops. Do you believe these numbers are trustworthy and verifiable or more likely false and exaggerated?

The Russian numbers are suspect for several reasons. Russian offensive operations have achieved only limited success in the last several months, with gains often measured in meters instead of kilometers, especially in heavily contested areas such as Bakhmut. [First], "official" Russian accounts of Ukrainian [and/or] international casualties are suspect because an accurate count would presume that Russia had captured significant swaths of territory. Second, [Russia's claim] that Ukrainian soldiers had abandoned their dead on the battlefield. Third, that recovered bodies carried passports or other documents to indicate that they were foreign volunteers.

But Russian gains have been small, and Ukraine has been scrupulous about recovering their dead and wounded. Thus, Russian claims are greatly exaggerated.

Why do you think Russia exaggerates Ukrainian losses, and is it possible to assess how significant these manipulations are?

The pressure for Russian military command to exaggerate Ukrainian casualties is intense. Despite massive numbers of Russian dead and the loss of thousands of tanks, armored vehicles, artillery systems and hundreds of aircraft, Russia is no closer to subduing Ukraine than it was at the beginning of its "special military operation" in February of last year.

Ukraine has reported more than 108,190 Russian troops have been killed in action. A rough estimate of the number of Russian soldiers wounded in this period would be north of 324,000. With Russian casualties approaching half a million, the need for Russia to report substantial Ukrainian losses is imperative, but the numbers of Ukrainian dead and wounded are only a fraction of Russian casualties.

Four-hundred-and-fifty thousand Russian casualties might seem high, but this estimate is bolstered by Russia's need to hastily mobilize 300,000-plus men during the last part of 2022. A second mobilization is slated to occur in the next two weeks. This one, as well, will call more than 300,000 Russian men to military service. These mobilizations are made necessary by heavy Russian casualties and tactical failure on the battlefield.

Ukraine does not announce its daily losses, but occasionally confirms total casualties. How accurate are their numbers?