The move gives Kim Jong-un, the leader of North Korea, leverage to ask President Vladimir V. Putin of Russia for a lot in return.

Russia's lower house of parliament ratified an overarching partnership treaty with North Korea on Thursday, as South Korea considers its response to North Korean troops in Russia. The partnership treaty takes military cooperation between the two countries to a new level and stipulates that they will provide mutual assistance should either country be attacked.

South Korea’s spy chief has told lawmakers that North Korea has sent another 1,500 troops to Russia to support its war against Ukraine.