HEADQUARTERS
Joint Task Force (JTF-SB)USNORTHCOM
Fort Huachuca, AZ 85613
May 2025
CONFIDENTIAL
From: C.O., 27th RLT
To: CMG, 1st MarDiv, (-) Rein.
Subj: Operation Sentinel Trace, 40-mile Vietnam War Style, Anti-Infiltration.
Ref. (a) MCO 5750.4
(b) FMF Pac 5750.8
(c) DivO 57550.2B
Encl: Operation Sentinel Trace, US Southern Border
1. In accordance with the above provisions of references (a), (b), and (c), enclosure (1) is submitted herewith.
PART I: ORGANIZATIONAL DATA
PART II: OPERATIONAL SUMMARY
PART III: LOCATION
PART IV: SEQUENTIAL LISTING
PART V: CIVIL AFFAIRS AND SECURITY
PART VI: CONCLUSION
PART VII: SUPPORTING DOCUMENTS
PART I: ORGANIZATIONAL DATA
1. Units Required to Construct/Maintain a Vietnam DMZ-Style McNamara Barrier Along the Southern US Border
a.) To replicate a Vietnam DMZ-style McNamara barrier along the southern US border, a combination of specific military and engineering units, as well as supporting assets, would be required. The historical McNamara Line utilized a blend of combat, engineering, surveillance, and support units, which can be adapted to a modern context as follows:
(1) Combat Engineers (e.g., US Army Corps of Engineers, Navy Seabees): Responsible for clearing land, constructing physical barriers (fences, ditches, bunkers), laying minefields, and building strongpoints and support bases. In Vietnam, Marine engineers and Navy Seabees bulldozed wide strips (the "Trace") and built strongpoints fortified with bunkers and wire obstacles.
(2) Infantry and Security Forces (e.g., US Marine Corps, Army Infantry, National Guard): Manned strongpoints, conducted patrols, and provided security for construction and maintenance operations. In Vietnam, thousands of Marines were deployed to man the strongpoints and patrol the barrier.
(3) Surveillance and Sensor Units (e.g., Military Intelligence, Signal Corps): Installed and monitored electronic sensors (seismic, acoustic, infrared) to detect movement and infiltration attempts. Managed data from sensors and coordinated rapid responses to detected incursions.
(4) Artillery and Fire Support Units: Positioned to provide immediate fire support to strongpoints and reaction forces in response to detected threats. In Vietnam, artillery positions were established along key routes to support the barrier.
(5) Aviation and Airborne Surveillance Units (e.g., Air Force, Army Aviation): Provided aerial surveillance, rapid troop deployment, and air support in response to barrier breaches or sensor alerts. Aircraft such as EC-121R were used to relay sensor data and coordinate responses.
(6) Logistics and Support Units: Ensured continuous supply of materials (barbed wire, mines, sensors), maintenance of infrastructure, and support for personnel stationed along the barrier.
1. The original McNamara Line, constructed during the Vietnam War (1966–1968), was a combination of physical barriers, fortified bases, minefields, and advanced electronic surveillance designed to prevent infiltration of North Vietnamese forces across the DMZ into South Vietnam.
a.) To adapt this concept to the southern US border, the system would blend retro defensive techniques with modern enhancements, focusing on creating a continuous anti-infiltration barrier.
2. Operation Sentinel Trace: A Retro-Style McNamara Anti-Infiltration Line for the Southern U.S. Border.
a.) Overview: Inspired by the Vietnam War’s McNamara Line, this conceptual operation—codenamed Operation Sentinel Trace—envisions a fortified, sensor-driven anti-infiltration barrier along the southern U.S. border. The goal is to prevent unauthorized crossings using a blend of physical obstacles, electronic surveillance, and rapid-response forces, echoing the Vietnam-era approach but adapted for the U.S.-Mexico border context.
3. McNamara Line/DMZ-Style Trace Features
a.) A cleared trace (strip) 500–600 meters wide, bulldozed and stripped of vegetation and structures.
b.) Fortified strongpoints and bases at intervals.
c.) Observation towers, bunkers, and fire support bases.
d.) Extensive barbed wire, minefields, and electronic surveillance (acoustic, seismic, and infrared sensors).
e.) Patrol roads and rapid response forces.
f.) Constant surveillance and rapid artillery/air response to detected incursions.
4. Application to the U.S. Southern Border
a.) Cleared Trace: A 500-meter-wide strip cleared of vegetation, running continuously for 40 miles between Sasabe and Nogales.
b.) Strongpoints: Fortified bases every 5–10 miles, with observation towers, bunkers, and rapid response teams.
c.) Sensors: Deployment of modern equivalents to Vietnam-era sensors—acoustic, seismic, infrared, and motion detectors—integrated with surveillance drones and cameras.
d.) Obstacles: Multiple layers of barbed wire, anti-vehicle trenches, and non-lethal minefields (e.g., sensors or noise-makers rather than explosives).
e.) Patrol Roads: Parallel access roads for rapid movement of border patrol and response forces.
5. Physical and Electronic Components
a.) Physical Barriers: Barbed wire, concertina wire, ditches, minefields, and fortified bunkers/outposts.
b.) Electronic Surveillance: Seismic, acoustic, infrared sensors, and night observation devices.
c.) Command and Control: Centralized facilities to process sensor data, coordinate responses, and manage overall barrier operations.
1. A 40-Mile Designated Trace Segment.
a.) A plausible 40-mile segment for constructing a Vietnam-era DMZ-style McNamara anti-infiltration trace would be along the U.S.-Mexico border in southern Arizona, specifically between the towns of Sasabe and Nogales.
b.) This area is known for high levels of cross-border movement and challenging terrain, making it a relevant candidate for a hypothetical strongpoint obstacle system.
2. Coordinates
a.) Western Terminus (near Sasabe, AZ): Approx: 31.4750°N, 111.5400°W.
b.) Eastern Terminus (near Nogales, AZ): Approx. 31.3320°N, 110.9440°W.
c.) This segment runs roughly east-west, closely paralleling the international border, and covers approximately 40 miles (64 kilometers).
3. Current Condition of the Sasabe-Nogales Corridor Wall
a.) The Sasabe–Nogales segment of the U.S.–Mexico border in Arizona is characterized by a mix of rugged terrain, existing border wall infrastructure, ongoing maintenance, and some new construction activity.
b.) Physical State of the Wall
(1) The area features miles of the 30-foot, rust-colored steel bollard wall constructed primarily during the Trump administration.
(2) The wall is highly visible and traverses challenging landscapes, including steep hills, washes, and desert vegetation.
(3) Despite the imposing barrier, there are known breaches and gaps in the wall, which are actively used by migrants and smugglers to cross into the United States.
c.) Recent Developments and Construction
(1) As of early 2025, there are reports of renewed border wall construction in Arizona, including the Nogales area, as part of broader efforts to close gaps and reinforce the barrier.
(2) The Biden administration had previously canceled contracts and repurposed leftover wall materials, but the current (second) Trump administration has signaled intentions to resume and complete wall construction, with some new contracts awarded for Arizona segments.
(3) Some border wall panels and materials have been removed or relocated as part of a congressional mandate to use, transfer, or donate surplus materials purchased with Department of Defense funds.
d.) The Sasabe–Nogales border wall segment is a dynamic zone with a substantial physical barrier, ongoing maintenance and repair, some renewed construction, and persistent challenges related to unauthorized crossings and environmental impacts.
4. Rationale for Segment Selection
a.) The Sasabe–Nogales corridor is a historically active region for unauthorized crossings and smuggling.
b.) The terrain is varied, with both open desert and rugged hills, presenting operational challenges similar to those faced in Vietnam.
c.) Proximity to existing infrastructure (Border Patrol stations, highways) allows for logistical support.
PART IV: SEQUENTIAL LISTING
1. Phase 1: Land Clearance and Initial Construction
a.) Timeline: Months 1–6.
b.) Military engineers (Army Corps of Engineers, National Guard, and Seabees) bulldoze a 60–100-meter-wide strip along key infiltration corridors, focusing on federal lands such as the Roosevelt Reservation.
c.) Construction of “Trace” (cleared strip), removal of vegetation, and initial emplacement of barbed wire and (non-lethal) minefields.
2. Phase 2: Strongpoint and Sensor Network Installation
a.) Timeline: Months 6–18.
b.) Establishment of fortified bases every 10–15 miles, each with bunkers, watchtowers, and rapid-response platoons.
c.) Deployment of electronic sensor arrays: seismic, acoustic, infrared, and motion detectors, linked to command centers for real-time monitoring.
d.) Installation of advanced surveillance (drones, thermal cameras, radar), and tripwire-triggered alarms.
3. Phase 3: Full Operationalization and Patrolling
a.) Timeline: Months 18–36
b.) Integration of air support (helicopters, drones) for rapid interdiction.
c.) Regular patrols by military units along the Trace, with Border Patrol responsible for arrests.
d.) Continuous maintenance, upgrades, and adaptation based on infiltration patterns.
4. Estimated Construction and Operating Costs
a.) The original McNamara Line, intended to span the DMZ and parts of Laos, had a construction budget estimated at $1.5 billion (1967 USD) and annual operating costs of $740 million.
b.) The system included physical barriers (mines, barbed wire, strongpoints), electronic surveillance (acoustic, seismic sensors), and supporting infrastructure.
c.) The annual operating costs for the barrier system were generally cited as close to $1 billion per year, not including research and development or command center expenses.
d.) The original project also included substantial research and development costs (about $1.6 billion) and a $600 million command center for operations in Laos.
e.) The effectiveness of the barrier was questionable, as North Vietnamese forces were able to bypass or defeat many of its components, and the system was abandoned after the Tet Offensive in 1968.
PART V: CIVIL AFFAIRS AND SECURITY
1. The region remains a hotspot for migrant crossings despite the presence of the wall, with migrants from diverse countries attempting to enter through gaps or by circumventing the barrier.
2. Cartel activity and the presence of armed vigilantes have been reported on both sides of the border, contributing to the complex security and humanitarian environment.
PART VI: CONCLUSION
1. The Sasabe–Nogales border wall segment is a dynamic zone with a substantial physical barrier, ongoing maintenance and repair, some renewed construction, and persistent challenges related to unauthorized crossings and environmental impacts.
2. This is a hypothetical scenario for illustrative purposes, based on historical precedent and current border geography. The actual implementation of such a system would involve complex legal, environmental, and political considerations.
3. Historical Parallels and Considerations
a.) The Vietnam McNamara Line featured a combination of physical barriers, electronic sensors, and strongpoints, but was ultimately hampered by cost, maintenance, and the adaptability of infiltrators.
b.) The U.S. southern border’s length (1,954 miles) and varied terrain would present similar logistical and operational challenges.
c.) Modern technology (drones, advanced sensors) offers improved surveillance and rapid response potential compared to 1960s-era systems.
d.) As in Vietnam, military units would support but not replace Border Patrol in law enforcement roles, maintaining a legal distinction.
PART VII: SUPPORTING DOCUMENTS
1. Summary Table: Sasabe–Nogales Wall Segment (April 2025)
| Feature | Current Status |
|---|---|
| Wall Structure | 30-foot steel bollard wall, miles-long, some gaps |
| Condition | Ongoing repairs, some erosion and damage |
| Construction Activity | New contracts awarded, some construction resuming |
| Surplus Materials | Some panels removed/relocated per congressional mandate |
| Migrant Crossings | Ongoing, through breaches/gaps and rugged terrain |
| Security Environment | Active Border Patrol, cartel presence, humanitarian aid |
| Environmental Concerns | Ongoing, especially near protected lands |
2. Summary Table: McNamara Line vs. Sasabe-Nogales Trace
| Feature | Vietnam DMZ (McNamara Line) | Hypothetical U.S. Border Segment (Sasabe–Nogales) |
|---|---|---|
| Length | ~47 miles (76 km) | 40 miles (64 km) |
| Width | 500–600 meters | 500 meters |
| Strongpoints | Every few miles | Every 5–10 miles |
| Sensors | Acoustic, seismic, infrared | Modern equivalents plus drones/cameras |
| Obstacles | Barbed wire, minefields | Barbed wire, anti-vehicle trenches, non-lethal sensors |
| Surveillance | Patrols, electronic monitoring | Patrols, electronic monitoring, rapid response teams |
3a. Construction Table: Assignments
| Unit/Agency | Role |
|---|---|
| Army Corps of Engineers | Land clearance, construction of barriers and strongpoints |
| National Guard | Patrols, quick reaction forces, logistics |
| U.S. Marine Corps/Seabees | Engineering support, fortification construction |
| U.S. Air Force | Aerial surveillance, drone operations |
| U.S. Border Patrol | Law enforcement, processing of detainees |
| Department of Homeland Security (DHS) | Coordination, intelligence, and oversight |
3b. Construction Table: Assignments
| Unit Type | Vietnam Example | US Border Equivalent Role |
|---|---|---|
| Combat Engineers | USMC Engineers, Seabees | Land clearing, barrier construction |
| Infantry/Security | USMC, Army Infantry | Manned strongpoints, patrols |
| Surveillance/Sensor Teams | Signal/Intelligence | Sensor installation and monitoring |
| Artillery/Fire Support | US Army/USMC Artillery | Fire support for barrier breaches |
| Aviation/Airborne Surveillance | EC-121R, Helicopters | Aerial surveillance, rapid response |
| Logistics/Support | Various | Supply, maintenance, sustainment |
4. Construction Table 002: Barrier System Components
| Feature | Description |
|---|---|
| Cleared “Trace” | 60–100 meter wide strip, denuded of cover for visibility and movement denial |
| Barbed Wire Fencing | Multiple layers, with concertina wire and anti-personnel obstacles |
| Minefields | Controlled, monitored, and marked for anti-infiltration (non-lethal focus) |
| Strongpoints | Fortified bases every 10–15 miles, manned 24/7 |
| Sensor Arrays | Seismic, acoustic, infrared, and motion sensors for real-time tracking |
| Watchtowers | Manned observation posts with searchlights and direct communication |
| Surveillance Drones | Persistent aerial monitoring and rapid response cueing |
| Rapid Reaction Forces | Mobile units stationed at strongpoints for immediate interception |
5. Comparative Chronology Table: McNamara Line, Sasabe-Nogales Trace
| Step | Vietnam DMZ (1967–1968)125 | Southern US Border (Retro-Style Plan) |
|---|---|---|
| Planning | Early 1967 | Months 1–3 |
| Land Clearance | Summer 1967, "The Trace" | Months 1–6 |
| Strongpoint Build | Fall 1967–Spring 1968 | Months 4–12 |
| Sensor Deployment | 1967–1968 | Months 7–18 |
| Full Operation | Late 1968 | Months 19–24 |
Report Data: Perplexity AI (Primary).
Image:
McNamara: https://veteransbreakfastclub.org/mcnamaras-line-the-limits-of-high-technology-in-the-vietnam-war/
McNamara Line:
https://webdoc.sub.gwdg.de/ebook/p/2005/CMH_2/www.army.mil/cmh-pg/books/vietnam/northern/nprovinces-ch2.htm
Border Wall: Perplexity AI.
JTF-SB 2025
3/LRC/cr1/5750
CMCC NR _____3______
Ser. No. 040-25
COPY _1__ OF __10__COPIES
21 April 2025
Prepared by: JCL, Pvt., (212xxxx-2533) USMC, 27th RLT-HQ, (AT998687)
End of Report.
CONFIDENTIAL