This is the first time that Russia has admitted that North Korean troops have been aiding them in their war against Ukraine:

Russian President Vladimir Putin has thanked North Korean leader Kim Jong-un for the deployment of troops to support its war with Ukraine, pledging that their bilateral friendship, forged on battlefields, will continue to grow in all areas, the Kremlin said Monday.
Putin conveyed his gratitude to Kim for the “active role” played by North Korean soldiers in the fight against Ukraine, his statement updated on the website of his office said, just hours after Pyongyang officially confirmed its troop deployment to Russia.
He praised the solidarity, justice and genuine camaraderie North Korean soldiers had shown, adding that “We highly appreciate this and are sincerely grateful, personally to the Chairman of State Affairs, Comrade Kim Jong-un, as well as the entire leadership and the people” of North Korea.
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