After briefly establishing himself as Emperor of China from 1915 to 1916, the death of dictator Yuan Shikai resulted in a period of political turmoil in China known as the Warlord Era, the most recent where country fell apart (again).
Along with territories already disputed with surrounding powers, China would lose effective control over Outer Mongolia until briefly reestablishing control from 1919 to 1921 and Tibet until 1951 after the fall of the Qing, rendering both regions de facto independent.
No cities of either of these two regions make the list with Lhasa being the largest of Tibet at 35,000 and Niislel Khüree (Ulaanbaatar) in Mongolia at 38,000.
A very good quiz, still challenging even for Chinese. Chixi is a surprising answer, because it seems to have always been an ordinary town, and it is hard to believe that it had a population comparable to that of some provincial capitals. At the same time, Shunqing seems to be an answer that should be revised, or at least accept "Nanchong" as the answer. Because the seat of Shunqing Prefecture in the Qing Dynasty has always been in Nanchong, and the administrative district name "Shunqing" has been abandoned since 1913. Nanchong is the name of the city that continues to this day.
Along with territories already disputed with surrounding powers, China would lose effective control over Outer Mongolia until briefly reestablishing control from 1919 to 1921 and Tibet until 1951 after the fall of the Qing, rendering both regions de facto independent.
No cities of either of these two regions make the list with Lhasa being the largest of Tibet at 35,000 and Niislel Khüree (Ulaanbaatar) in Mongolia at 38,000.