McKean's previous assignments include tank platoon leader and company executive officer in the 3rd Battalion, 73rd Armor Regiment and operations officer for the XVIII Airborne Corps Long Range Surveillance Company at Fort Bragg, North Carolina, as well as posts at Camp Red Cloud, Korea.[10] He was also a tank company commander and headquarters company commander in the 4th Battalion, 64th Armor Regiment at Fort Stewart, Georgia.
McKean served as the operations officer and executive officer for the 1st Battalion, 67th Armored Regiment, 4th Infantry Division, during his deployment to Iraq. Later, he assumed duty as the deputy G3, 4th Infantry Division and deployed to Baghdad. He then commanded the 1st Battalion, 66th Armor Regiment and deployed back to Baghdad. He deployed again as the commander of the 4th Armored Brigade Combat Team, 1st Armored Division in 2011 as part of Operation New Dawn in Iraq.[11]