Preparing for Survival Retreat Perimeter Defense, by O.F.

Friday, Oct 17, 2008

There may come a time when a survival retreat will need to be defended, and a properly prepared perimeter will be key to the success of the defense. While many survival-minded individuals and retreat groups have likely considered the possibility of a defense scenario, many are at a loss as to how to plan for such an situation. If the time comes, a well-thought, methodically planned perimeter defense will hold up better than simply having “a bunch guns and ammo.”


Fighting positions offer several advantages during perimeter defense. Proper positions allow the defenders to observe possible threats with reduced risk of detection, protect the defenders from attack, and serve as a point of reference for reporting events to other members of the retreat. They also form a buffer between the outside world and the retreat. Fighting would-be attackers at “arm's length” is preferred to fighting them inside the retreat, because it keeps the threat away from important assets and personnel.
Fighting position placement will vary widely depending on terrain, but should always be done with 360 degree security as the goal. Follow the acronym OCOKA [Observation and fields of fire, Cover and Concealment, Obstacles, Key terrain, and Avenues of approach } when considering terrain:

Observation and Fields of Fire – Positions need to be located so that the area outside the perimeter may be observed in all directions. Fields of fire/observation (or sectors) should overlap. For example, if one position is observing 12 o'clock to four o'clock, then the next position might observe three o'clock to seven o'clock. Other positions would cover similar sectors ensuring the entire “clock” is observed.

Cover and Concealment – Cover is protection from projectiles or other forms of attack. Natural cover, such as logs, dirt berms, or stone are advantageous in a rural or remote environment since they blend in and are often readily available. Man-made cover could include vehicles, retaining walls, sand bags, furniture, or dumpsters. Concealment is protection from observation. Good positions offer defenders a place to hide to avoid being detected and blend in with their environments.

Obstacles – Obstacles force attackers to slow down, stop, or change direction when trying to approach a fighting position. Some natural obstacles include downed trees, cliffs, ravines, streams, boulders, and embankments. Some man-made obstacles include fences, road barricades, concertina wire, parked vehicles, debris piles, berms, and ditches.

Key terrain – Key terrain is any piece of terrain which offers a definite advantage to whoever occupies it. For example, a hill overlooking the retreat would provide obvious advantages for anyone wanting to defend or attack it. Other key terrain features might include intersections of roads or paths leading to the retreat, areas affording excellent cover or concealment, or supply storage buildings.

Avenues of approach – Positions should be able to monitor the roads, paths, waterways and open areas which offer access to the retreat. Attackers are much more likely to come up a driveway than through a forest heavily overgrown with brush. The farther the visibility on avenues of approach, the more warning defenders will have.

After determining where to emplace fighting positions, available personnel must be taken into consideration. If only two or three people will be defending the perimeter, then it may not make sense to build a dozen positions. Even with a dozen people, not everyone will be able to man the positions all the time. Everyone needs to rest some time, so personnel will need to man the positions in shifts. In such a scenario it would probably be better to setup half a dozen fighting positions which could each be occupied by two people at times if needed. If the situation necessitates more fighting positions than available personnel can occupy, then decoys can be placed in unmanned positions.

Equipment will also be a factor in preparing fighting positions. A backhoe can easily dig a foxhole in mere minutes, whereas it may take an hour or more with e-tools or spades. There may only be enough sandbags on hand to fortify a few positions. Different types of weapons work better in some locations than in others. Don't put the only sniper rifle on the retreat at a position that will be guarding a 100-meter approach up a ravine if there is a position overlooking half a mile of road leading to the driveway. Yours should balance caliber, range, and rate of fire around the perimeter where they will be most effective.

Once the terrain, equipment and personnel considerations have been made, the type of fighting position should be selected. As there is an inverse relationship between the protection offered by a position and the time it takes to construct, the type of position chosen will depend on the opportunity cost between the two. The basic types of fighting positions suited for most retreats will be the hasty, the one-man position, and the foxhole. Each will be described briefly here. For more detailed information, see the following US Army Field Manuals: FM 7-8 (Infantry Rifle Platoon and Squad) andFM 3-21.9 (The SBCT Infantry Rifle Platoon and Squad).

Hasty positions – These positions consist of nothing more than a shallow trench just large enough for a defender to lay prone. The hasty offers no overhead protection and little protection to the front or flanks, but it is the quickest to construct. If there is plenty of time to prepare, then pick a different option. Ideally, one position should consist of two trenches aligned in a V so that two people may occupy it and cover a wider sector (each prone in one leg of the V).

One-man positions – These positions are usually holes just large enough for one person. Cover and concealment can be added to protect the defender. Positions with only one person are the not as desirable as positions with two or more because they leave one person responsible for an entire sector. If something should happen to that one person, then the perimeter would have a gap. If using one-man positions, locate them within site of each other.

Foxholes – Possibly the most recognized fighting positions, foxholes are two-man pits which are the ideal choice for perimeter security. Foxholes should be dug approximately two meters by half a meter and armpit-deep to the tallest defender (shorter individuals will have to stand on something). This will ensure the best cover and natural shooting positions will be afforded to all personnel. Cover and concealment should be added to the fronts and sides of the hole, leaving the two front corners somewhat open for observation/fire.

Create a sector sketch for each position. Draw a pie wedge which represents what the position's field of observation/fire looks like from the perspective of the person occupying it. Include direction and distance notations. Draw in trees, buildings or other obstructions and label dead space which cannot be viewed behind these obstructions. This information can be used for planning interlocking sectors of fire with other positions. Post a copy of the sketch in the fighting position, so that anyone occupying it has an idea of what they are responsible for watching and where the trouble spots are.
Also, keep a copy or each position's sketch at the retreat command post (CP) for “big picture” planning and situational awareness.

Fighting positions on the perimeter, once established, should be continually improved. Sectors [of security responsibility] should be cleared of objects limiting lines of site. Cover should be added to the front, sides, rear, and top of the positions. Camouflage should be checked by walking out 50 to 100 meters and observing the position; if it doesn't blend well with the background it will have to be improved. Communication equipment should be added. TA-312 field telephones or similar closed-circuit devices are a good choice. If practical, stock fighting positions with first aid kits, ammunition, water and other supplies. Details and changes should be added to sector sketches. Crawl trenches can be added between fighting positions for a safe way to move between them.

After fighting positions are well-established, extend the perimeter with obstacles. Put concertina wire or brush 50 to 150 meters beyond fighting positions. Add serpentine barriers or speed bumps to roads or paths. Fell trees across unused avenues of approach. Put up fences. Anything that makes the perimeter harder to breach should be considered.

Early warning systems alert defenders to a possible attack. It's better to have some advance notice that someone is coming than to be caught by surprise. Some early warning systems are active (require personnel to function). Once such system is a listening post/observation post (LP/OP). LP/OPs are positions which are strategically placed outside the perimeter in a locations which offer observation of a likely line of attack. The object of LP/OPs is usually not to engage attackers, but rather to communicate back to defenders on or inside the perimeter about suspicious activity or pending attacks before trouble reaches the perimeter. Since communication is an LP/OPs biggest weapon, each one should have at least two forms of communication if available. LP/OPs should be camouflaged to the maximum extent possible. Individuals manning the LP/OP should be well disciplined at light and noise discipline to further avoid detection.

Passive early warning systems do not require constant attention from personnel to function. Ordinarily this might include a security system or even a dog that always barks when a stranger approaches the house. A retreat perimeter defense scenario may call for some less conventional options. Passive early warning devices need to be easy to build, effective, and require little maintenance. Trip wires are cheap, and meet these requirements. A simple trip wire can be constructed from "Spiderwire" (or other high-tensile, low-visibility filament), a plastic spoon, a clothespin, and WD-1 commo wire (other stranded pair wire, such as speaker wire, will work). Construct the trip wire [release switches] as follows:

  1. Split apart a several inches of the two WD-1 elements and strip back a few inches of the insulation on both wires.
  2. Pinch open the clothes pin and wrap the exposed wire from one element of the WD-1 around one jaw of the clothespin. Do the same with the other element and the other jaw of the
    clothespin. When the clothespin closes, the two exposed elements should be in contact.
  3. Tie the clothes pin to a fixed object.
  4. Tie the spoon handle to a piece of Spiderwire (you probably want to drill a small hole in the spoon handle).
  5. Clip the bowl part of the spoon in the jaws of the clothespin in order to insulate the two exposed wires from touching each other.
  6. Tie the other end of the Spiderwire to another fixed object across the path, thus forming the trip wire (it should be taut enough to stay suspended across the path, but not so tight that the spoon
    pulls out of the clothespin).
  7. Connect the far end of the WD-1 to the the device to be triggered.

Tripping the line causes the spoon to be pulled out of the clothespin and the exposed wires to touch each other. This completes the circuit at the far end of the wire. This simple switch can be used to activate flares, lights, or alarms.

If no alarm circuits are available, improvised devices like the following may be fashioned. (Check state and local laws, first!):

20 oz bottle blast alarm:

  1. Drill a small hole in a the top of the bottle cap.
  2. Insert an Estes model rocket igniter (available at hobby shops) into the hole and seal with adhesive or melted plastic (cut off the safety seal ring from the cap and melt with a lighter)
  3. Fill the cap nearly full with [FFF or FFFF black] gunpowder.
  4. Pack dryer lint into the cap on top of the powder.
  5. Screw the cap tightly onto the bottle.
  6. When the two ends of the rocket igniter are attached to a power source (6-volt battery
    should be enough) the bottle will explode with a loud bang.


Fuse flare (homemade flash pot, similar to devices available at theatrical shops):

  1. Carefully break and remove the glass in a screw-in [AC electric] fuse. (the kind used before circuit breakers were the norm in American houses).
  2. Use tin snips to cut 3⁄4 of the way through the metal strip in the fuse.
  3. Screw the fuse into an ordinary lamp socket (socket should be pointed upwards).
  4. Place photographic flash powder (available at theatrical supply stores) in the fuse.
  5. When power is applied to the fuse body, the flash powder will create a bright flash of light.
  6. A piece of Scotch tape will help keep the powder in the fuse
  7. Use model rocket igniters or fine gauge (0000) ] steel wool connected to the electric leads to light the fuse.

[JWR Adds: Although this improvised method will work, it is both expensive and labor intensive. I recommend stocking up on large 1960s-vintage photographic flashbulbs, such as Westinghouse M2 bulbs. These are available on eBay for as little as 40 cents each, if purchased in quantity. (One recent eBay auction was for 300 "new old stock" M2 flashbulbs and the winning bid was just $77.) You might also be able to find similar flashbulbs via Craig's List or Freecycle. BTW, if you use extreme caution (gloves, safety goggle, et cetera), a hole can be drilled into some flashbulbs, so that a pyrotechnic fuse can be inserted into the mesh core. This allows flashbulbs to double as fuse igniters. Resist the urge to trickle in blackpowder to create a blasting cap. This is far too risky!]

Roman candles or other fireworks:

  1. Use model rocket igniters or [a thin twist of fine gauge (0000)] steel wool connected to the electric leads to ignite the fuse on the firework.
  2. Tape the wires securely to keep them from being dislodged.

A standard operating procedure (SOP) should be developed after the perimeter infrastructure is in place. The best perimeter infrastructure in the world is useless if those defending it are uncoordinated. The SOP should address who will occupy each fighting position and what their areas of responsibility are. It should also specify when, how, and who will perform other critical security tasks including patrolling the perimeter for weak spots, checking communications equipment, re-supplying or redistributing ammunition in the event of an active engagement, treating casualties, rotation of challenges and passwords, length of guard shifts, and anything else that is imperative to the specific retreat. All members of the retreat should be familiar with the SOP, and defensive scenarios should be practiced on a regular basis, preferably by battle drills or at least by talking through the process with the aid of diagrams or sand tables.

While having to resort to defending a retreat is not desirable and may not seem likely, it is still a realistic possibility. Taking the time to build a well planned perimeter defense will be a real advantage in the event of an attack. Going without a plan could be chaotic at best, and cost precious supplies or lives at worst.


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