Complex sentence: In the 1970 general elections Biharis predominantly supported the mostly-West Pakistani Muslim League over the Awami League (overwhelmingly supported by Bengalis), and played an active anti-secessionist role in the liberation war.
Split into simpler sentences: In the 1970 general elections, Biharis predominantly supported the mostly West Pakistani Muslim League, in contrast to the Awami League which was overwhelmingly supported by the Bengalis. They played an active anti-secessionist role in the liberation war.