Platt served in this capacity until December 1952 and then was ordered for combat duty to Korea.
He joined 5th Marine Regiment, 1st Marine Division and served under Colonel Lewis W. Walt as commanding officer of 1st Battalion.
His battalion was stationed on the Main line of resistance (MLR) in Western Korea and tasked with the defense of "Nevada Cities" – systems of bunkers and outposts on the MLR, which oversaw the enemy's rear.

The Chinese communists forces activity consisted mainly of patrolling and there was no significant enemy activity.
However situation has changed in the night on March 26, 1953, when Chinese launched offensive against outposts Vegas, Carson, and Reno.
Under constant enemy artillery and mortar fire and with no contact with front units, Platt and his battalion had keep their sector and drove all Chinese troops back to their lines.

In mid-April 1953, regimental commander, Colonel Walt, was appointed 1st Marine Division Operations officer.
Aware of Platt's organizational qualities, he requested him to be attached to the operations section under his command.
Platt relinquished command of 1st Battalion to lieutenant colonel Jackson B. Butterfield on April 29, 1953, and joined Divisional Operations section (G-3).
He served in this capacity during the battle of the Samichon River in July of that year and following the Korean Armistice Agreement signed on July 27, Platt participated with the division in the guarding of the newly created Korean Demilitarized Zone.
He was finally ordered back to the United States in mid-September 1953 and received the Legion of Merit with Combat "V" for his service in Korea.
Platt served in this capacity until December 1952 and then was ordered for combat duty to Korea. He joined 5th Marine Regiment, 1st Marine Division and served under Colonel Lewis W. Walt as commanding officer of 1st Battalion. His battalion was stationed on the Main line of resistance (MLR) in Western Korea and tasked with the defense of "Nevada Cities" – systems of bunkers and outposts on the MLR, which oversaw the enemy's rear.
The Chinese communists forces activity consisted mainly of patrolling and there was no significant enemy activity. However situation has changed in the night on March 26, 1953, when Chinese launched offensive against outposts Vegas, Carson, and Reno. Under constant enemy artillery and mortar fire and with no contact with front units, Platt and his battalion had keep their sector and drove all Chinese troops back to their lines.
In mid-April 1953, regimental commander, Colonel Walt, was appointed 1st Marine Division Operations officer. Aware of Platt's organizational qualities, he requested him to be attached to the operations section under his command. Platt relinquished command of 1st Battalion to lieutenant colonel Jackson B. Butterfield on April 29, 1953, and joined Divisional Operations section (G-3). He served in this capacity during the battle of the Samichon River in July of that year and following the Korean Armistice Agreement signed on July 27, Platt participated with the division in the guarding of the newly created Korean Demilitarized Zone. He was finally ordered back to the United States in mid-September 1953 and received the Legion of Merit with Combat "V" for his service in Korea.
Jonas M. Platt