Jim,
As with any obstacle, roadblocks will only be effective if covered by fire. Also obstacles must be tied into the terrain and the overall fighting plan. Digging an anti-tank ditch across a road [in level country] won’t stop anyone if they can just drive around it. The French Maginot Line was a great obstacle, but the Germans just went around it. So any roadblock has to tie into other natural or artificial barriers. A roadblock that denies the only bridge that crosses an otherwise impassible river is a good example of one that ties into the terrain. However, if that obstacle is not covered by fire, then it only provides a delay. An enemy will still reach it’s objective, it just might take longer. It’s pretty simple. If there is no covering fire, then the obstacle can be reduced sooner or later. A tree across a road might stop a truck, but a few sandbags on each side and a truck can get over it. If no one is there to provide “discouragement”, then the obstacle will be breeched. Adequately covering that tree with fire prevents it’s reduction, and the obstacle prevents mobility. So each enhances the other. Also, the obstacle has to be sufficient for the desired effect. The tree has to be big enough, or the wall tall enough, or the river deep enough, etc. The Alamo had one portion of it’s wall that was very weak and thrown up at the last minute. While covered by fire, it was inadequate for what was needed, and this is where the Mexican Army was able to breech the fortress by concentrating force at the weak spot. So think obstacle, not speed-bump.
In your defense planning, remember that an obstacle NOT covered by fire will not STOP anyone.
Use OCOKA (Observations and fields of fire, Cover and Concealment, Obstacles, Key terrain, Avenues of approach) when you analyze the terrain. Tie your obstacles in with your overall fighting plan. They’re just one tool in the box, and must be used with other tools to get the job done. By themselves, they do nothing but cause you to expend resources on them. Tie them in with your retreat defense plan. – “Doug Carlton”
James:
A point that I raise with heavy equipment is not a new one, but important to know. Most manufacturers, (even to this day) have one key, (meaning all matching door knobs, ignitions, etc…) for that brand. This means in simple terms, if you own a CASE skid loader, then you can start everyone else’s too. Not much for piece of mind!
As a kid, I remember my Dad sticking the old Ford pickup keys about 1/4″ into the dozer ignition and voila! It starts. He ended up putting a push button start in a secret place and it took the key and the button to start it. I would hate to have a D4 dozer aimed at my retreat no matter the construction!
-The Wanderer
JWR Replies: I’m sorry that I did not make myself clear. It almost goes without saying that to be relatively “immobile” a vehicle needs to have its ignition system rendered useless. This is best accomplished by removing a key part. (which will vary, according to the engine and ignition type.) In regard to Doug’s comments: A great description of the futility of constructing roadblocks that are not covered by small arms fire is described in the Larry Niven and Jerry Pournelle’s novel “Lucifer’s Hammer.”