Complex sentence: In 1982 al-Mourabitoun militia defended with doggedness Beirut, besieged by the Israeli army, and this during 3 months, and continued its resistance to the occupation, up to the withdrawal of Israeli troops of the Lebanese capital.
Split into simpler sentences: In 1982 al-Mourabitoun militia defended Beirut, besieged by the Israeli army over a period of 3 months. It continued its dogged resistance to the occupation up to the withdrawal of Israeli troops from the Lebanese capital.