Complex sentence: In 1820 he departed for Peru as part of an expeditionary force of liberators and on arrival fought in many major battles, including the Battle of Junín and the Battle of Ayacucho.
Split into simpler sentences: In 1820 he departed for Peru as part of an expedition of liberators. There he fought in many of the campaign's major battles, including the Battle of Junín and the Battle of Ayacucho.