Complex sentence: When he was released, the HuA had been included in the US list of Foreign Terrorist Organisations which had compelled the outfit to rename itself as the Harkat-ul-Mujahideen (HuM).
Split into simpler sentences: When he was released, the HuA had been included in the US list of Foreign Terrorist Organisations. This compelled the outfit to rename itself the Harkat-ul-Mujahideen (HuM).