A veteran of World War II, he distinguished himself as platoon leader of the 3rd Battalion, 25th Marines, during the Iwo Jima campaign and received the Silver Star for bravery.

[1] Simlik served as rifle company commander under Lieutenant Colonel Jonas M. Platt and later assumed duty as battalion operations officer.

[3][1][2] Following his return to the United States at the end of July, Simlik remained on active service and was appointed officer-in-charge, Marine Corps Recruiting Station in Portland, Oregon.

While in this capacity, he was promoted to the rank of major in December 1954 and held that command until August 1956, when he rejoined the 1st Marine Division at Camp Pendleton, California.

Simlik graduated in January 1959 and assumed duty as special projects officer, Analysis and Review Branch, Fiscal Division, at Headquarters Marine Corps and was promoted to the rank of lieutenant colonel in July 1960.

He subsequently remained there as an instructor in the Supporting Arms Branch for brief period, before sailing for Okinawa, Japan for duty with the 3rd Marine Division under Major General James M. Masters Sr.[1][2] He served as divisional assistant operations and training officer until August 1964, when he was ordered to Naples, Italy, for duty as commanding officer of Marine barracks at Naval Supply Activity there.

PAVN activity within the area of operations was light at the beginning, consisting of sporadic rocket attacks against Marine installations, sniper contacts, and attempts at interdicting Routes 9 and 561 with mines and other surprise firing devices.

Operation Idaho Canyon lasted until the end of September that year, and Simlik's 3rd Marines counted 563 PAVN killed and 201 weapons captured.

[4][1][2] Now due to the withdrawal information, nobody wanted to be the last man killed in battle and the situation was worsened by journalists, who segregated some black Marines and asked them suggestive questions if they did more than your share.

[4] During the last week of September, the 3rd Marines were moved to Đông Hà Combat Base and then departed for the United States.

Simlik then served for one month as deputy chief of staff, 3rd Marine Division, under Major General William K. Jones.

But his tour of duty in South Vietnam was not finished, and he was subsequently ordered to Da Nang, where he joined the headquarters, III Marine Amphibious Force under Lieutenant General Herman Nickerson Jr. as assistant chief of staff for logistics (G-4).

Simlik was placed on the retired list on September 1, 1975, but was returned to active duty without interruption of service to continue as fiscal director until November 15, 1975.

[9] Simlik was a member of Rotary Club of Vista and was active in the Marine Corps Historical Foundation, where he received a certificate of appreciation by Commandant Robert H. Barrow for his contributions to the Oral History Program.