North Korea’s entry into Russia’s war against Ukraine is a major escalation in the grinding conflict, but Moscow may find it’s more trouble than it’s worth.

The recently signed mutual defense treaty could be used to justify thewidening of the war in Ukraine, as the U.S. says North Korean and Russian troops are already battling Ukrainian forces.

SEOUL, South Korea (AP) — North Korea ratified a major defense treaty with Russia stipulating mutual military aid, the North’s state media reported Tuesday, as the U.S., South Korea and Ukraine say North Korea has sent thousands of troops to Russia to support its war against Ukraine.

Captured Russian soldiers have revealed the presence of North Korean troops fighting in Ukraine under Vladimir Putin’s command. The prisoners of war (POWs) shared these details during interrogations by Ukrainian forces.