Activated with the 5th Marines during the United States build-up for World War I. The battalion deployed to France and took part in major AEF-era Marine actions including Belleau Wood, Soissons, St. Mihiel, Blanc Mont, and Meuse-Argonne.
Unit History / Infantry Battalion
3rd Battalion, 5th Marines
“Darkhorse” is the infantry-battalion reference lane for the command archive. The public lineage traces organization to 8 June 1917, service in France during World War I, and later campaigns across the Pacific, Korea, Vietnam, Southwest Asia, Iraq, and Afghanistan.
Parent Formation5th Marine Regiment · 1st Marine Division
Home StationCamp Pendleton, California
HISTORY
Public Historical Breakdown
Reactivated in the early 1920s, served in Caribbean and mail-guard missions, and deployed to Nicaragua during the late 1920s before a later deactivation and pre-World War II reactivation.
Served in the Pacific campaigns, including Guadalcanal, New Guinea, Peleliu, and Okinawa, before postwar deactivation.
Reactivated in 1949 and deployed to Korea in 1950, adding Pusan Perimeter, Inchon, Seoul, and Chosin Reservoir to its record. From 1966 to 1971 the battalion fought in Vietnam across locations including Chu Lai, Da Nang, Quang Nam, Que Son, An Hoa, and Ross Combat Base.
Deployed as a Battalion Landing Team in 1990, distinguished itself in Kuwait during Operation Desert Storm, and then supported Operation Sea Angel relief efforts in Bangladesh.
Deployed to Iraq in 2003 and 2004, including Fallujah and Operation Phantom Fury. Its Afghanistan record includes Operation Enduring Freedom service in 2010–2011.
MOS
Common MOS Lanes
3/5 serves as the infantry foundation: rifle companies, weapons Marines, infantry leaders, infantry officers, and green-side corpsmen attached to Marine ground units. The 3/5 Darkhorse infantry side is treated as part of the 3/5 Darkhorse lane, not as a separate Unit History page.
PIPELINE
Training Pipeline Overview
Enlisted Infantry
Recruit training is followed by infantry training at the School of Infantry. Public SOI material describes ITB as training and certifying Marines as riflemen, machine gunners, mortarmen, infantry assaultmen, and anti-tank missilemen for service in the operating forces.
Weapons MOS
Weapons-track Marines build from common infantry foundations into crew-served weapons, anti-armor, and unit weapons employment before joining a line or weapons company.
Infantry Officers
Officer candidates commission, complete The Basic School, then progress into infantry officer training before leading platoons or serving on infantry battalion staffs.
Green-Side Corpsmen
Navy corpsmen assigned to Marine units complete Marine-oriented field medical training, then support rifle companies, weapons elements, battalion aid stations, and deployed ground formations.
PROFILE USE
Assignment Lane
Current Assignment Only
This unit lane controls background art, insignia, and active-unit identity for profiles assigned here. Individual names stay inside the Chain of Command system.
Clean Historical Page
Unit history pages focus on lineage, mission, MOS lanes, training pipeline, and public references. Personal biography details stay on the member profile.
COMPANIES / PLATOONS
3/5 Darkhorse Task Organization
3rd Battalion, 5th Marines is the ground-combat baseline for sustained infantry operations, combined-arms maneuver, force protection, terrain seizure, and security tasks in support of SOTF objectives.
Headquarters Company
Provides battalion command and control, intelligence fusion, personnel administration, communications, planning support, and mission-command continuity across battalion elements.
India Company
Conducts offensive and defensive infantry operations, security tasks, sector control, and force-protection missions to secure maneuver space and protect high-value assets.
Kilo Company
Executes deliberate assaults, expeditionary security, area denial, and terrain-hold missions to rupture enemy formations and preserve freedom of movement.
Lima Company
Conducts raids, cordon-and-search, support-by-fire, isolation, and shaping actions that enable precision engagement by maneuver and specialist elements.
Rifle Platoons
Patrol, move to contact, attack, defend, conduct convoy protection, search-and-clear, immediate-action response, NEO/PEA-style security, and point-security tasks.
Weapons Company
Provides mortars, precision engagement, observer/JTAC coordination, EOD/IED mitigation, and amphibious scout support to maneuver commanders.
Mortar Platoon
Delivers responsive indirect fires and fire-support coordination to suppress, neutralize, and shape enemy activity before and during maneuver.
Observer / JTAC Platoon
Coordinates and controls joint and close-air support, integrating aviation and precision fires against prioritized targets.
Sniper Platoon
Provides long-range precision engagement, overwatch, reconnaissance-by-observation, target development, and high-threat denial.
EOD Platoon
Conducts explosive hazard clearance, IED mitigation, render-safe procedures, and freedom-of-movement support for maneuver elements.
Amphibious Scout Teams
Conduct shore reconnaissance, small-boat movement, littoral observation, and maritime approach support for amphibious or interdiction operations.
SOURCES