When was the Mongolian People’s Republic proclaimed and how did it change the capital’s name?

The Mongolian People’s Republic was proclaimed in November 1924, following the adoption of the country’s first constitution by the Great Khural, which met from November 8 to 26.1

During this same period, the capital city—previously known as Niislel Khüree—was renamed Ulaanbaatar (also spelled Ulan Bator), which translates to "Red Hero". This change honored the revolutionary leader Damdiny Sükhbaatar, whose forces, alongside the Soviet Red Army, had captured the city in 1921.12