Cmdr. Cassidy was commissioned in July of 1999 and began flight school in Pensacola, FL. After winging, he was assigned to Patrol Squadron 10 (VP-10) in Brunswick, ME and made two deployments. He was assigned to Fleet Support Unit 5 (FSU-5) for Littoral Surveillance Radar System (LSRS) missions, then aboard the USS George Washington (CVN 73), and following that he entered the Naval War College (NWC) as a student in the junior class. His next posting was as a department head in Patrol Squadron 5 (VP-5) making two deployments. This was followed by two posting to the College of Operational and Strategic Leadership (COSL) at NWC and one tour as the Commander, U.S. Navy Region Korea (CNFK) N5.