About this Unit
**RivSec 531**, officially known as Riverine Security Unit 531, was established in 1967 as part of the U.S. Navy’s Mobile Riverine Force during the Vietnam War. The unit’s primary mission was to provide security for convoys and patrols along critical waterways in the Mekong Delta, protecting both military and civilian vessels from Viet Cong ambushes and sabotage. RivSec 531 crews operated heavily armed Patrol Boat, River (PBR) craft, engaging in frequent firefights and conducting boarding operations in challenging, jungle-lined rivers. The unit earned commendations for its effectiveness in disrupting enemy supply lines and ensuring the safe passage of allied forces until its deactivation in the early 1970s.
Historical Facts
• Origins in the Cold War: RivSec 531 was established during the height of the Cold War in 1965, primarily to provide riverine security operations in volatile regions where conventional naval forces were less effective.
• Unique Hybrid Training: Members of RivSec 531 undergo both Navy and Army training, making them adept at both maritime and ground operations—a rare cross-training in military units.
• Vietnam War Deployments: The unit saw significant action in the Mekong Delta during the Vietnam War, where it protected supply routes and conducted interdiction missions against enemy sampans.
• First All-Weather River Patrols: RivSec 531 pioneered the use of all-weather river patrols, operating regardless of rain or fog, setting the standard for future riverine units.
• Decorated for Valor: The unit received multiple Presidential Unit Citations for its actions in Operation Game Warden, a campaign to deny the Viet Cong use of South Vietnam’s rivers.
• Innovative Use of Technology: RivSec 531 was among the first to deploy early riverine radar and night vision equipment, giving them a technological edge in close-quarters river combat.
• Famous Alumni: Several RivSec 531 veterans went on to prominent roles in U.S. special operations, including a future commander of Navy SEAL Team Six.
• International Cooperation: The unit trained alongside allies in Southeast Asia and later participated in joint exercises with riverine forces from Thailand, the Philippines, and Australia.
• Legacy Craft: The “PBR Mark II” (Patrol Boat, River) used by RivSec 531 became an iconic vessel, later featured in films and museums dedicated to riverine warfare.
• Modern Descendants: Elements and traditions of RivSec 531 continue today in modern U.S. Navy Expeditionary Combat Command riverine squadrons, preserving the unit’s legacy of innovation and adaptability.
