Complex sentence: On September 9, President Doe paid a visit to the barely established headquarters of ECOMOG in the Free Port of Monrovia, was at the ECOMOG headquarters attacked by INPFL, taken to the INPFL's Caldwell base, tortured and killed.
Split into simpler sentences: On September 9, President Doe paid a visit to the barely established headquarters of ECOMOG in the Free Port of Monrovia. While he was at the ECOMOG headquarters, he was attacked by INPFL, taken to the INPFL's Caldwell base, tortured and killed.