South Korea’s military says it suspects North Korea is preparing to send additional troops to Russia after its soldiers already deployed on the Russian-Ukraine war fronts suffered heavy casualties.

North Korea may be accelerating plans to send more troops to replace frontline casualties incurred fighting Ukraine on behalf of Russia.

The attack came as South Korea’s military said North Korea is preparing to send more troops to join Russia’s fight against Ukraine, despite Pyongyang suffering a high rate of losses among its existing deployment of 11,000 and seeing some of its soldiers captured.

Ukrainian forces described a different kind of enemy, fighting with unfamiliar tactics and little option to retreat.

Russia signed a strategic partnership treaty with Iran on Friday that follows similar pacts with China and North Korea. All three countries are adversaries of the United States, and Russia has used its ties with them to help blunt the impact of Western sanctions and boost its war effort in Ukraine.