Colonel Jonathan Nicklas Sims earned his commission from the Officers Candidate Course after graduating from Texas University with a Bachelor Degree in Economics. Upon graduation from The Basic School in December 1998, he reported to Ft Sill, Oklahoma for instruction in the United States Army Field Artillery Basic Officers Course. Graduating in June 1999, Colonel Sims reported for duty with Battery S 5th Battalion, 10th Marines in Camp Lejeune, North Carolina. He served as a Forward Observer, Liaison Officer, Fire Direction Officer, and Executive Officer. During this tour he completed a six month deployment to Okinawa and Camp Fuji, Japan as part of the Unit Deployment Program.
In May of 2002, Colonel Sims reported to the Naval Postgraduate School in Monterrey, California as a student to complete his Master of Business Administration in Defense Systems Analysis. Upon graduation, he was assigned to Headquarters Marine Corps, Programs and Resources in the Pentagon as the Land Forces Analyst. He served there from January to May 2004, when he was nominated as an individual augment to advise the Iraqi Army. He deployed to Baghdad, Iraq as an Infantry Company Advisor to the 2d Battalion, 1st Brigade Iraqi Intervention Force. During this period, he participated in combat actions in Southern Baghdad, An Najaf, and Fallujah. Following this tour, he returned to Programs and Resources in January 2005 where he served as Division Analyst for the 2006 Quadrennial Defense Review and as a modeling and simulation risk assessor for budget formulation.
Colonel Sims reported to 1st Battalion 10th Marines as the Commanding Officer of Battery B. Upon aggregation of the 22d Marine Expeditionary Unit, Colonel Sims attached his battery to Battalion Landing Team 3/8. During the deployment, he served as Commander of Troops on board the USS PONCE. Following the deployment and change of command, he was assigned as the Officer in Charge of Military Transition Team 130 (3d Brigade, 1st Iraqi Quick Reaction Force) in May 2008. From September 2008 to September 2009, Colonel Sims and his team conducted combat operations with their Iraqi Brigade initially in Diyala and then for 11 months in Mosul. Upon completion of this tour, he reported to the College of Naval Command and Staff at the Naval War College, Newport, Rhode Island from October 2009 to October 2010.
After graduation, Colonel Sims returned to Camp Lejeune as the Executive Officer for 2d Battalion 10th Marines, where he served until July 2011. Then he joined Regimental Combat Team 6 and deployed with them in December 2011 until November 2012 to Helmand Province, Afghanistan. During this assignment, he served as the Afghan National Security Forces Director and Future Operations Officer. He served in combat operations in the Washir, Kajaki, and Musa Qala Districts. Upon return from deployment, he served as the 6th Marine Regiment Operations Officer until October 2013.
In November 2013, Colonel Sims was assigned to Marine Corps Security Cooperation Group in Ft Story, Virginia. From then until May 2015, he served as the European Command Coordination, Liaison, Advise and Training Team Officer in Charge. During this tour, he led security cooperation focused training for the Georgian Deployment Program and Black Sea Rotational Force as well as serving as the operations officer for multiple Republic of Georgia Mission Rehearsal Exercises.
In June 2015, Colonel Sims assumed command of 1st Air Naval Gunfire Liaison Company (1st ANGLICO). From then until June of 2017, he deployed teams in support of West Coast MEUs, deployed to Saudi Arabia, Iraq, and Syria in support of combat operations, and conducted theater security cooperation with Japanese, Taiwanese, Singaporean, Mexican, Canadian, Malaysian, and British military forces.
In July 2017, Colonel Sims reported as a student to the College of International Security Affairs at National Defense University. Here he studied counterinsurgency and counterterrorism with fellow students from over 50 different countries and 20 different US government agencies.