It is the oldest and largest active duty division in the United States Marine Corps, representing a combat-ready force of 22,000 personnel.

Between April 1914 and August 1934, elements of the 1st Brigade participated in operations in Mexico, Haiti, the Dominican Republic, and Cuba, receiving campaign credit for service in each nation.

[5] In May 1941, the 1st MARDIV relocated to Quantico, Virginia and Parris Island, South Carolina and in April 1942, the division began deploying to Samoa and Wellington, New Zealand.

The division's units were scattered over the Pacific with the support elements and the 1st Marine Regiment transported en route to New Zealand on three ships, the USATs Ericsson, Barnett and Elliott from Naval Reserve Air Base Oakland to New Zealand,[6] and later were landed on the island of Guadalcanal, part of the Solomon Islands, on 7 August 1942.

[8] Due to the change in orders and shortage of attack and combat cargo vessels, all of the division's 2.5-ton trucks, M1918 155-mm howitzers[9] and the sound and flash-ranging equipment needed for counter-battery fire had to be left in Wellington.

[10] After 11 days of logistical challenges, the division, with 16,000 Marines, departed Wellington in eighty-nine ships embarked for the Solomon Islands with a 60-day combat load which did not include tents, spare clothing or bedrolls, office equipment, unit muster rolls, or pay clerks.

They came ashore at the Battle of Cape Gloucester on 26 December 1943[17] and fought on New Britain until March 1944 at such places as Suicide Creek and Ajar Ridge.

"[19] Making a mockery of the prediction, the first week of the battle alone cost the division 3,946 casualties, during which time they secured the key airfield sites.

The strategic importance of Okinawa was that it provided a fleet anchorage, troop staging areas, and airfields in close proximity to Japan.

Most Marines in the division would be charged with guarding supply trains, bridges, and depots to keep food and coal moving into the cities.

During this time they increasingly fought skirmishes with soldiers from the People's Liberation Army who raided ambushed, and harassed the railways and other infrastructure.

[31][32] By the summer of 1946 the division was suffering the effects of demobilization and its combat efficiency had dropped below wartime standards; however, its commitments in China remained.

[31] Following the end of World War II and the postwar drawdown of forces, by 1950 the division only possessed the strength of a reinforced regimental combat team.

After the liberation of Seoul, the division was put back on ships and taken to the eastern side of the Korean peninsula and landed at Wonsan on 26 October.

As part of X Corps commanded by Army Major General Edward Almond the division was ordered to push north towards the Yalu River as fast as possible.

They fought their way out of the Chosin Reservoir against seven PVA divisions suffering over 900 killed and missing, over 3,500 wounded and more than 6,500 non-battle casualties mostly from frostbite during the battle.

The greater part of the PVA 9th Army was rendered ineffective as they suffered an estimated 37,500 casualties trying to stop the Marines' march out of the "Frozen Chosin".

By June 1951 the 1st Marine Division had pushed northward and secured the Punchbowl and then settled into a defensive line 11 miles (18 km) long.

[40] The 1st Marine Division was reassigned to the far western end of the MLR defending a 35 miles (56 km) line that encompassed the Pyongyang to Seoul corridor.

[42] In August 1965, the division's 7th Marine Regiment participated in Operation Starlite, the first major engagement against the Vietcong (VC) for American ground troops in South Vietnam.

[48]: 63–8  From May to June the 5th Marine Regiment conducted Operation Union II with Army of the Republic of Vietnam (ARVN) forces.

[51]: 103–16  From 26 May to 7 November Division, ARVN and Republic of Korea Marine Corps (ROKMC) units conducted Operation Pipestone Canyon on Go Noi Island.

[53]: 69–76  From 1 September to 7 May 1971 Division and ROKMC units conducted Operation Imperial Lake in the Quế Sơn District south of Da Nang.

[53]: 238  On 30 April President Richard Nixon welcomed the division back to Camp Pendleton and awarded it a second Presidential Unit Citation for its service in South Vietnam.

[55] In 1990, the 1st Marine Division formed the nucleus of the massive force sent to the Middle East in response to Iraq's invasion of Kuwait.

During Operation Desert Shield, the division supported I Marine Expeditionary Force (I MEF) in the defense of Saudi Arabia from the Iraqi threat.

U.S. Marine involvement in Operation Restore Hope officially ended on 27 April 1993, when the humanitarian relief sector of Mogadishu was handed over to Pakistani Armed Forces.

"[60] Initially, the division fought through the Rumaila oil fields, feinted an attack towards Basrah[61] then moved north on Iraq Highway 1 to An Nasariyah – a moderate-sized, Shi'ite dominated city with important strategic significance as a major road junction and proximity to nearby Talil Airfield.

The division covered 808 kilometers in 17 days of sustained combat,[62] the deepest penetrating ground operation in Marine Corps history.

The 2nd Marine Division originally had a similar battle blaze of the same design with a red snake in the shape of a "2" also reading GUADALCANAL.