 The acceptance of the reimbursement was enough to convince Jennison to hand down a death sentence.Even before the start of hostilities Jennison became a captain of the Mound City Guards on February 19, 1861.Although not with Senator James H. Lane's Kansas brigade during the Sacking of Osceola, Jennison was associated with it and would soon join the fray after receiving a commission as colonel from Kansas Governor Charles L. Robinson on September 4.