Complex sentence: Appointed commander of Greek forces in Anatolia by Constantine in late 1920, however his offensive to establish Greek control over western Anatolia was halted at the First Battle of Inonu in January 1921.
Split into simpler sentences: Appointed commander of Greek forces in Anatolia by Constantine in late 1920. However his offensive to establish Greek control over western Anatolia was halted at the First Battle of Inonu in January 1921.