Simplify the following text for a Grade 15 native English-speaking person.
Original: Zakarpattia Oblast was formally established on 22 January 1946 after the annexation of the Transcarpathian Hungary to the Ukrainian Soviet Socialist Republic to fulfill the petition filled by the Carpatho-Ukraine before the World War II .
Simplified: Zakarpattia Oblast was formally established on January 22 , 1946 after the annexation of Subcarpathian Rus lands to the Ukrainian Soviet Socialist Republic .