Complex sentence: In 1925, high commissioner General Maurice Sarrail, in preparation for upcoming elections, allowed the organization of political parties, and the Syrian factions of the Syrian-Palestinian Congress, which had proved itself an ineffectual body, returned to Syria.
Split into simpler sentences: In 1925, in preparation for upcoming elections, high commissioner General Maurice Sarrail allowed the organization of political parties. The Syrian-Palestinian Congress had proved itself an ineffectual body, and its Syrian factions returned to Syria.