North Korea’s decision to support Russia’s invasion of Ukraine is part of a “sacred mission” to counter U.S. influence around the world, according to state-run media.

At a training site in Russia, the five North Korean soldiers had grins on their faces and guns in their hands. Then they began singing a cappella, belting out a Soviet-era song called “Katyusha" about a young woman bidding farewell to soldiers—in translated Korean-language lyrics.

North Korean leader Kim Jong Un said North Korea’s involvement in the Russia-Ukraine war was justified, calling it an exercise of sovereign rights in defence of a “brother nation,” state media KCNA reported on Saturday.