Major Gretchko is a native of Ohio. He attended The Ohio State University, graduating in 2005. Major Gretchko enlisted in the United States Marine Corps in May 2005 and attended 3rd Recruit Training Battalion aboard MCRD Parris Island, SC. He graduated recruit training in August of 2005 as a Private First Class and was transferred to Camp Geiger, NC for Infantry Training where he earned the MOS 0311. In December 2005 Private First Class Gretchko checked in to Lima Company, 3rd Battalion 25th Marines in Columbus, Ohio where he served for approximately one year and attained the rank of Lance Corporal.
In October 2006 Major Gretchko was selected to attend Officer Candidates Course 193, and completed Officer Candidates School in December 2006, receiving his commission as a Second Lieutenant. In January 2007 Second Lieutenant Gretchko reported to The Basic School on Marine Corp Base Quantico, VA and completed training with Bravo Company in July 2007.
After completing The Basic School, Second Lieutenant Gretchko reported to Naval Air Station Pensacola, FL for Introductory Flight Screening and subsequently to Training Squadron Twenty Seven in Corpus Christi, TX and Helicopter Training Squadron Twenty-eight in Pensacola, FL for flight training. Designated a Naval Aviator in November 2009, he received orders to Marine Medium Helicopter Training Squadron 164, MCAS Camp Pendleton, CA and attended the Fleet Replacement Squadron (FRS) for the CH-46E Sea Knight.
First Lieutenant Gretchko checked into HMM-364 “Purple Foxes” in August 2010, serving multiple billets in the squadron Logistics and Operations departments. From September 2012 to May 2013, Captain Gretchko deployed in support of the 15th Marine Expeditionary Unit (MEU). Upon return, Captain Gretchko attended Aviation Safety Officer (ASO) School and served as the squadron NATOPS Officer and ASO.
In May 2014 Captain Gretchko was selected to transition to the MV-22B Osprey, and attended the FRS at MCAS New River, NC. Upon completion of the MV-22B FRS, he returned to HMM-364 to serve as an initial cadre of pilots standing up VMM-364 in October 2015. From April to October 2017, Major Gretchko deployed in support of Special Purpose Marine Air Ground Task Force-Crisis Response-Central Command, where he served as the Director of Safety and Standardization.
In April 2018 Major Gretchko received order to Marine Aircraft Group (MAG) 26, Jacksonville NC. He served as the MAG-26 Personnel Support Detachment Commanding Officer from May to June 2018 before being transferred to VMM-365 “Blue Knights”, where he served as the Operations Officer. From October to November 2018 Major Gretchko deployed in support of Exercise Trident Juncture 2018, the largest NATO exercise of its kind in nearly 30 years. From December 2019 to July 2020 Major Gretchko served as the Logistics Officer while deployed with the 26th MEU. Major Gretchko is currently the Executive Officer for VMM-365.