Complex sentence: The Conciliators emerged in the mid- 1920s from the "middle group" around Ernst Meyer in the Communist Party of Germany (KPD), which along with the faction led by Ernst Thälmann, formed the leadership of the KPD from 1926 to 1928.
Split into simpler sentences: The Conciliators emerged in the mid- 1920s from the "middle group" around Ernst Meyer in the Communist Party of Germany (KPD). Along with the faction led by Ernst Thälmann, they formed the leadership of the KPD from 1926 to 1928.