Formed during World War I, it served until the mid-2000s when it was deactivated to make room for one of three light armor reconnaissance battalions.

During the Vietnam War, 1/9 sustained an especially high casualty rate as they faced extraordinary challenges and hardships during their tour.

General Võ Nguyên Giáp promised President Ho Chi Minh that he would wipe out the 1st Battalion, 9th Marines, as a present for the leader's birthday (May 19, 1966).

In describing the fate that awaited the Marines in the valley, Giap allegedly used the term "Di Bo Chet", translated as the "Walking Dead".

However, 1st Battalion, 9th Marines, proudly and defiantly adopted "The Walking Dead" as its nickname due to the unit's persistence and resilience.

In late 2005, the battalion was reactivated and attached to the 8th Marine Regiment at MCB Camp Lejeune; additionally, Motor Transport Drivers and Mechanics were assigned to Headquarters Company, 6th Marine Regiment, Camp LeJeune.

As of 29 August 2014 the battalion has been deactivated due to a force shaping initiative and downsizing of the Marine Corps.

During the Vietnam War, the unit earned the name "The Walking Dead" for its high casualty rate.

[3] The battalion endured the longest sustained combat and suffered the highest killed in action (KIA) rate in Marine Corps history, especially during the Battle of July Two.

The battalion was engaged in combat for 47 months and 7 days, from 15 June 1965 to 19 October 1966 and 11 December 1966 to 14 July 1969.

The Marines and Sailors were trained in Counter Terrorism, Downed Airman Rescue, Embassy evacuations, SPIE rigging, fast roping, rubber raiding in their inflatable boats for boarding and insertion, and rappelling.

1st MEB was disestablished when the 22nd MEU (SOC) was reassigned to the Mediterranean area of operations in mid-November.

During this time, the company conducted security and stabilization operations north of Al Khalis in the Diyala Governorate, working jointly with Military Police, Cavalry and Field Artillery units from the National Guard.

From September, 2012 to December, 2012, Alpha Company deployed to Ahmad al-Jaber Air Base, Kuwait, providing security forces for MAG-40.