Simplify the following text for a Grade 9 native English-speaking person.
Original: Facing permanent internal and external problems , the young state was unable to withstand the invasion by the Russian SFSR Red Armies , and collapsed between February and March 1921 to become a Soviet republic .
Simplified: Facing permanent internal and external problems , the young state was not able to withstand the invasion by the Russian SFSR Red Armies . It collapsed between February and March of 1921 to become a Soviet republic .