North Korean leader Kim Jong Un cheered on Russia’s “sacred war” on Ukraine while celebrating liberation from Japan on Thursday, according to state media, exchanging letters with Russian leader Vladimir Putin and making a rare visit to a war monument celebrating the Soviet army.

It was the first time Kim marked the Aug. 15 Liberation Day holiday by visiting the Liberation Tower in Pyongyang, more prominently acknowledging the Soviet Union’s role in retaking the peninsula when Japan surrendered in 1945 in a reflection of their flourishing ties.