In the meantime, the Chinese had imprisoned a number of members and sympathizers of the secret group. In late 1920, White Russian forces under Lieutenant General Baron Ungern had entered Mongolia from the east, and in late February 1921 occupied Niislel Khüree. Choibalsan and Chagdarjav were sent back into Mongolia to establish contacts with nationalist-minded nobles and other leaders. On February 9, Sükhbaatar was appointed commander-in-chief of the Mongolian People's Partisans. He began recruiting soldiers, and on February 20 the partisans had their first engagement with Chinese troops, followed by other encounters in the following days. At the founding congress of the Mongolian People's Party (MPP) at Kyakhta on March 1–13, 1921, Sükhbaatar was again appointed commander-in-chief and elected into the newly established provisional government.