Simplify the following text for a Grade 8 native English-speaking person.
Original: In January 1920 , the town was surrounded by a partisans force nearly four thousand strong under the command of anarchist Yakov Triapitsyn , who was loosely allied with the Bolshevik Red Army .
Simplified: In January 1920 , the town had been surrounded by an army of four thousand controlled by Yakov Triapitsyn , who was allied with the Red Army .