North Korean soldiers fighting for Russia have reportedly suffered significant losses.Although the troops are believed to be elite forces, they've been used similarly to Russian prison units.The soldiers appear to have been removed from combat.North Korean forces sent to fight Russia's war appear to be the latest in a growing line of disposable troops that have been torn apart in its fight against Ukraine.The troops sent to fight in Kursk are believed to be some of North Korea's more dedicated, better-trained soldiers, but they have suffered heavy losses in bloody "human wave" assaults. Ukraine's military has said that these forces haven't been seen in weeks, speculating that their high casualties may have led to them being withdrawn.South Korea's intelligence agency supported these observations, per local media, saying there have been no signs of the North Korean forces engaging in combat in Kursk in weeks. The National Intelligence Service said that the high losses could be the reason they were pulled off the front line, but they're looking into it.Expendable armies Russia has suffered high casualties throughout its war on Ukraine. Anadolu via Getty Images Russia's war against Ukraine has devastated entire Russian military units, from elite forces to poorly trained conscript units, butchered convict armies, and wiped out mercenary forces. Like the North Korean troops, many of these forces have been described as "cannon fodder" or simply "meat."The brutal Wagner mercenary group, which relied heavily on prisoners, lost an estimated 20,000 fighters in the fight for Bakhmut. Russia's Storm-Z penal units, which are basically convict forces, experienced high losses in front-line fights as well.Last year, the British Ministry of Defense accused Moscow of "wasting lives in a grotesque approach that typifies the depths to which President Putin's regime is prepared to go." Now, North Korean forces seem to have experienced a similar fate.Over 11,000 North Korean soldiers, mostly special operations forces, deployed to Russia's Kursk region last November in the wake of Ukraine's shock invasion of Russian territory.Later, once the North Korean troops had seen actual combat, the Biden White House said that the soldiers were involved in front-line assaults in Kursk and were being treated "as expendable." A Ukrainian commander who faced the North Koreans in battle told Business Insider they were basically "cannon fodder."Western and South Korean intelligence have tracked the reported casualties. The latest estimates put losses at around 4,000. The Institute for the Study of War think tank recently estimated that the entire contingent could be killed or wounded by April if current casualty rates were to continue. But North Korean forces no longer appear to be on the front line.The Russian way of war Russian soldiers fight against Ukrainian forces in Russia's Kursk region in November. Russian Defense Ministry Press Service via AP In a talk hosted by the Center for Strategic and International Studies on Tuesday, Seth Jones, president of the defense and security department at CSIS, said that the reported casualties were astonishing and that the soldiers are seemingly being used in ways similar to Russia's prison units, especially in Kursk, where the goal is to retake the territory Ukraine has seized and fortified."That's the way it appears that the Russians have used North Korean forces," Jones said, noting Russia has done this with higher-end forces as well. "This is the Russian way of war," he said. "It is stunning in the high-casualty component of it."Last month, Jones and Benjamin Jensen, a fellow at CSIS' future lab and a professor at the Marine Corps University of Advanced Warfighting, wrote in an op-ed for The Wall Street Journal that although a majority of North Korean forces appear to have come from its elite Storm Corps, they're being used for mine clearance and frontal assaults on fortified Ukrainian positions. This isn't a primary function of special operations units. North Korea's direct entry into the Ukraine war marked a new elevation in the conflict. KCNA via REUTERS Russia has shown improvements in its wartime tactics. Itselectronic warfare and use of uncrewed systems have developed rapidly. It has also advanced its reconnaissance strike complex. But the way it approaches retaking territory and engages in attritional warfare with many losses continues.A slow, grinding, attritional fight is not one that works to Ukraine's advantage, as Russia has more bodies it can commit to its war machine. Even as Ukraine continues to hold a significant portion of the territory it captured in Kursk, Russia has turned up the pressure, making it more difficult to hold. Moscow doesn't have an endless supply of bodies though.Russia's human wave assaults, vicious tactics with roots in old Soviet doctrine, have been documented throughout the war. They're intended to strain and overwhelm enemy defenses, but they come at extreme costs.The estimates for Russian killed and wounded in this war have been as high as 800,000. Western intelligence has tracked increasingly high daily losses, especially at the end of last year. The North Korean soldiers appear to now be being added to those losses. Neither the Russian embassy nor the Russian defense ministry responded to BI's requests for comment.A bloody partnership North Korean forces have reportedly not been seen on the front lines in weeks. Kim Won-Jin / AFP When North Korea deployed troops to fight for Russia, it appeared to signal a next step in a growing partnership. North Korean leader Kim Jong Un and Russian President Vladimir Putin have negotiated a mutual defense pact, as well as arms deals.Along with combat forces, North Korea has delivered ammunition and other weapons to Russia. What Kim could be getting in returnremains highly speculative, but possibilities include certain space and satellite capabilities, as well as food, petroleum products, and help with its air force and submarines. North Korea is also getting critical insights into how its weapons, including both artillery and missiles, perform in battle and valuable lessons in the ways of modern warfare.Jones said that it appears Pyongyang offered troops to Moscow rather than react to a request, but it's unclear if North Korea fully understood how its troops would be used. For Putin, the benefit of using North Korean troops, much like Wagner and other forces, is the ability to avoid a contentious mobilization at home.The South Korean Joint Chiefs of Staff said last month that Pyongyang may be planning to deploy additional forces and military equipment to Russia. In recent weeks, though, North Korean forces have been absent from the front lines, potentially due to heavy losses. It's unclear, though, if that is temporary or permanent.