"The scale of deployed North Korean troops is being closely watched," Yoon Yeocheol, South Korea's ambassador to the U.K., told Newsweek.

On the one hand, the deployment of the North Korean troops seems a logical follow-up to the mutual defense treaty signed by Kim Jong-un and Vladimir Putin in Pyongyang in June. On the other hand, it raises a series of important questions.

North Korea may deploy as many as 100,000 troops to aid Russia’s war on Ukraine if the alliance between Pyongyang and Moscow continues to deepen, according to people familiar with assessments made by some Group of 20 nations.