Reports that North Korean troops have already arrived in combat zones bordering Ukraine have raised alarm about their rapid deployment in support of Russia’s invasion, as well as questions about how the allies are transporting thousands of DPRK soldiers to the front lines.

South Korea, the U.S. and others have assessed that Russia transported North Korean personnel to training centers in the Far East earlier this month, but these troops would still need to travel thousands of miles to fight in Eastern Europe.

While Russia commonly uses trains to transport soldiers across its vast territory, NK Newsanalysis suggests that