Complex sentence: There he became active in the Missouri Volunteer Miltia (MVM), and in 1861 was appointed as lieutenant colonel commanding the MVM's Southwest Battalion, patrolling the Kansas border to protect Missourians from raids by bands of Kansas Jayhawkers.
Split into simpler sentences: There he became active in the Missouri Volunteer Miltia (MVM). In 1861 he was appointed as lieutenant colonel commanding the MVM's Southwest Battalion, patrolling Missouri's western border against raids by bands of Kansas Jayhawkers.