1st Combat Engr Bn, USMC--Command Chronology--Task Force Sapper, Anti-Infiltration Trace.
HEADQUARTERS
1st Combat Engineer Battalion
1st Marine Division (Rein) FMF
Camp Pendleton, California 92055
1ST ENGR BN3/LRC/cr1 5750
CMCC NR ___________ Ser. No. 040-25 COPY___OF_____COPIES20 April 2025
CONFIDENTIAL
From: Commanding Officer
To: Commanding General, 1st Marine Division (Rein) FMF
Subj: Command Chronology for the period March to April 2025
Ref: (a) MCO 5750.2
(b) FMF Pac 5750.8
(c) DivO 5750.2B
Encl: (1) 1st Combat Engineer Bn. Chronology
1. In accordance with the above provisions of references (a), (b), and (c), enclosure (1) is submitted herewith.
1ST COMBAT ENGR. BN.
COMMAND CHRONOLOGY
PART I: ORGANIZATIONAL DATA
PART II: NARRATIVE SUMMARY
PART III: SEQUENTIAL LISTING OF SIGNIFICANT EVENTS
PART IV: SUPPORTING DOCUMENTS
PART I: ORGANIZATIONAL DATA
1. DESIGNATION COMMANDER LtCol T.A. Barrion
SUBORDINATE UNITS
H&S Company
Support Company
Company "A" (Rein)
Company "B" (-) (Rein)
Company "C" (Rein)
2. LOCATION
a. Camp San Mateo, Camp Pendleton, CA.
b. Otay Mesa, Southern California Border
c. Federally designated military installation: Roosevelt Reservation.
3. STAFF OFFICERS
Executive Officer-
Sergeant Major-
S-1/Adjutant-
S-2-
S-3-
S-4-
S-5-
Supply Officer-
Communications Officer-
Medical Officer-
M.T. Officer-
M.T. Maintenance Officer-
Engineer Equipment Officer-
Utilities Officer-
Construction Officer-
AVERAGE MONTHLY STRENGTH
OFF-
ENL-
CASUALTY REPORT
15 April 2025:
(Non-combat related death, vehicle accident, Santa Teresa, NM) Lance Cpl. Albert A. Aguilera, 22, of Riverside, California, was a combat engineer with 1st Combat Engineer Battalion, 1st Marine Division.
(Non-combat related death, vehicle accident, Santa Teresa, NM) Lance Cpl. Marcelino M. Gamino, 28, of Fresno, California, was a combat engineer with 1st Combat Engineer Battalion, 1st Marine Division.
PART II: NARRATIVE SUMMARY
Task Force Sapper, Anti-Infiltration Trace
1. (San Ysidro, CA) During the months of March-April 2025, the 1st Combat Engineer Battalion (-) was instrumental in support of Joint Task Force Southern Border operations.
a.) U.S. Marines with 1st Combat Engineer Battalion, 1st Marine Division, assigned to Joint Task Force - Southern Border, reinforce the southern border barrier by welding engineer stakes to place concertina wire along the barrier near San Ysidro, California on April 9, 2025. Under the direction of U.S. Northern Command, Joint Task Force–Southern Border aligns efforts to seal the southern border and repel illegal activity and is responsible for full-scale, agile, and all-domain operations, which will allow for more effective and efficient DoD operations. (Sgt. Kimberly Villigran)
b.) U.S. Marines, with 1st Combat Engineer Battalion, 1st Marine Division, reinforce the southern border barrier near San Ysidro, Calif., Jan. 27, 2025. U.S. Northern Command is working together with the Department of Homeland Security with the emplacement of physical barriers to add additional security that will curtail illegal border crossings. (Sgt. Kimberly Villigran)
c.) U.S. Marines, with Task Force Sapper, deploy concertina wire along the southern border barrier near Otay Mesa, Calif., March 7, 2025. USNORTHCOM is working together with the Department of Homeland Security with the emplacement of physical barriers to add additional security that will curtail illegal border crossings. (Lance Cpl. Nataly Espitia)
Source: (U.S. Marines support southern border mission, 04 April 2025,
https://www.dvidshub.net/unit/DoDSWB25)
PART III: SEQUENTIAL LISTING OF SIGNIFICANT EVENTS
1. Personnel
a. Gains and Losses//OFF/ENL
2. Intelligence
a. Road and Bridge Reconnaissance
Aggressive patrols and border monitoring for interdiction.
b. Weather
Marked by intermediate spells of heat and monsoon rain.
c. Mine Warfare
a. n/a
b. n/a
d. Total ordnance destroyed
(1) n/a
(2) n/a
3. Training
a. n/a
b. n/a
c. n/a
d. Classes
(1) Communications
(2) Counter-intelligence
(3) Tactical bridges
(4) Legal Affairs
4. Operations
a.) Task Force Sapper- support unit, border security. (See Part II, Narrative Summary).
5. Water Supply
6. Construction
a.) Border support. (See Narrative Summary)
7. Civil Affairs/Civic Action
a.) Task Force Sapper: See Part IV: After Action Report)
8. Religious Affairs
9. Research and Development
PART IV: SUPPORTING DOCUMENTS
After Action Report: Task Force Sapper.
Task Force Sapper is a military unit composed primarily of U.S. Marines and Sailors, notably from the I Marine Expeditionary Force. As of 2025, the task force consists of approximately 500 personnel who have been assigned to support operations along the U.S. southern border.
Mission and Activities
Task Force Sapper has been tasked with providing logistics and engineering support as part of the broader Southern Border Mission.
Their activities include reinforcing border barriers by deploying concertina wire and other fortifications near locations such as San Ysidro and Otay Mesa, California.
These operations are conducted under the direction of U.S. Northern Command and as part of Joint Task Force–Southern Border, which coordinates all-domain operations to enhance border security and deter illegal activity.
Sapper Role in the Military
The term "sapper" refers to elite combat engineers skilled in a variety of military engineering duties, including minefield placement and clearing, construction of tactical support structures, demolition, and more.
Sappers are recognized for their expertise in mobility, counter-mobility, and survivability tasks, making them critical to both offensive and defensive military operations.
The U.S. Army Sapper Leader Course is a rigorous 28-day program that develops these skills and leadership abilities among combat engineers.
In March and April 2025, Task Force Sapper has been actively involved in reinforcing the southern border by installing concertina wire and supporting infrastructure improvements.
Their efforts are part of a larger, agile response to evolving border security challenges, providing both physical barriers and rapid engineering solutions.
The Otay Mesa border wall refers to a significant section of the United States–Mexico border barrier located in the Otay Mesa area of San Diego, California. This stretch is part of what is colloquially called the "Tortilla Wall," a 14-mile (22.5 km) segment running from the Otay Mesa border crossing to the Pacific Ocean. The wall was originally completed in the early 1990s and is the longest continuous border wall section in the region
a. Structure and Features
The wall near Otay Mesa consists of both a primary and a secondary fence.
The secondary fence is approximately 30 feet tall and constructed of vertical metal bollards
The area is heavily monitored and patrolled, with frequent use of surveillance and rapid response by U.S. Border Patrol agents.
b. Summary Table
Feature
Description
Location
Otay Mesa, San Diego, CA to Pacific Ocean
Length
14 miles (Tortilla Wall section)
Height
~30 feet (secondary fence)
Construction
Vertical metal bollards, electrical conduit on top
Key Incidents
Fatal falls, rescues of stuck individuals
Effectiveness
Major drop in apprehensions post-construction
Criticism
Shifts crossings to more dangerous areas; symbolic debate
Recent Developments
New port of entry construction, prototype wall testing
c. Conclusion
The Otay Mesa border wall is a prominent and heavily fortified section of the U.S.–Mexico border, designed to deter illegal crossings but also associated with significant risks for migrants. It remains a focal point for border security operations, humanitarian concerns, and cross-border economic activity.
