How did the Trans-Mongolian Railway connect Mongolia with Russia and China?

The Trans-Mongolian Railway serves as Mongolia's primary transportation artery, running north-south through the center of the country to link Russia and China. Built as a joint venture, the railway utilizes the Russian broad-gauge track width and is divided into two main sections:1

• Northern Section: Completed in 1949, this segment extends from the Russian border through Darkhan to the capital, Ulaanbaatar.1
• Southern Section: Completed in 1955, this segment runs from Ulaanbaatar to Zamyn-Üüd on the Chinese border.1

At the border crossing in Zamyn-Üüd, trains must undergo a wheel exchange to transition from the Russian broad-gauge system to China’s standard-gauge system. By providing a direct north-south corridor, the railway offers the shortest overland route between Moscow and Beijing. In addition to its international role, the line connects key Mongolian industrial and mining centers, such as Erdenet and Sharyn Gol, to the national and international rail network.123