About this Unit
The 3rd Battalion, 5th Marines (3/5), known as "Darkhorse," was activated in 1917 and served with distinction in World War I, participating in the legendary Battle of Belleau Wood. During World War II, 3/5 fought in major Pacific campaigns, including Guadalcanal, Peleliu, and Okinawa. The battalion played critical roles in the Korean and Vietnam Wars, earning numerous unit citations for valor and effectiveness. In recent years, 3/5 deployed to Iraq and Afghanistan, notably enduring heavy combat in Sangin, Helmand Province, where it upheld its reputation for courage and resilience.
Historical Facts
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Formation and Legacy: The 3rd Battalion, 5th Marines (3/5), also known as "Darkhorse," was first activated in June 1917 and has maintained a proud legacy as one of the most decorated battalions in the Marine Corps.
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World War I Valor: 3/5 fought in iconic battles such as Belleau Wood and Château-Thierry in France, earning its first Presidential Unit Citation for heroism under fire.
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Pacific Theater in WWII: The battalion participated in major campaigns including Guadalcanal, Peleliu, and Okinawa, suffering heavy casualties but playing pivotal roles in each victory.
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Korean War "Frozen Chosin": 3/5 was part of the legendary "Chosin Few," fighting in brutal conditions at the Chosin Reservoir and helping to lead the epic breakout, earning another Presidential Unit Citation.
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Vietnam War Service: From 1966 to 1971, 3/5 saw extensive combat in places like Hue City during the Tet Offensive, with Marines distinguishing themselves in street-to-street fighting.
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Modern Deployments: The battalion has been deployed to Iraq and Afghanistan in the Global War on Terrorism, notably during Operation Phantom Fury (the Second Battle of Fallujah) in 2004 and Operation Enduring Freedom in 2010–2011.
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"Darkhorse" Nickname: The nickname "Darkhorse" originated from the radio call sign of the battalion’s commanding officer during the Korean War and has since become a proud symbol for the unit.
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Innovative Tactics in Afghanistan: During their 2010–2011 deployment to Sangin, Afghanistan, 3/5 adapted to an environment filled with IEDs by pioneering new counter-IED tactics and strategies, saving many lives.
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Heavy Losses in Sangin: The battalion suffered significant casualties in Sangin, losing 25 Marines and a Navy Corpsman in just a few months—one of the highest loss rates for any Marine battalion in the Afghanistan conflict.
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Honoring the Fallen: The story of 3/5’s sacrifice in Sangin inspired numerous tributes, including the viral "Darkhorse" poem and the naming of facilities and memorials in their honor, reminding future generations of their valor and resilience.
