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If An Abatis Falls in a Forest, But the Enemy Didn't Observe It, Did It Really Happen?

To continue my series on “Guidelines versus Rules,” I am going to deconstruct what I call the "all obstacles must be observed" rule. Simply put, the most effective obstacles--like mine fields, tank ditches or IEDs--have someone somewhere observing them (usually with the ability to call for indirect fire).

Example: imagine a Brigade trying to cross a field with a river on the far side. The bridge crossing the river is destroyed, the field is mined, and tank ditches block the far end. A nightmare scenario. The defending force will rain down fire as the Brigade tries to cross the river, clear the field, and get over the tank ditches. The Soldiers aren't just trying to clear the obstacles; they're trying to avoid getting killed.

Obstacles observed by fire are dramatically more effective, both for and against you. If you place an obstacle, you should observe it. If you come across an obstacle, you should assume the enemy is observing it. This is why it is a good guideline: all obstacles, when possible, should be observed.

This good guideline, unfortunately, became a rule. It is a rule because many officers and planners are under the mistaken assumption that every obstacle must always be observed. During countless training exercises, I have seen planners say that either an obstacle shouldn’t be constructed because it can’t be observed, or that the enemy would not place an obstacle if he couldn’t observe it. I have heard field grade officers say, “If you can’t see the obstacle it might as well not be there."

A lot of the confusion comes from the definition of two terms. In Army doctrine, a simple obstacle is not observed. A complex obstacle is observed by fire. (IEDs are the same way. A simple IED ambush does not have direct fire supporting it. A complex IED does.) I believe the "every obstacle must be observed" rule developed because complex obstacles are more desirable then simple obstacles, so it became a habit to observe every obstacle. The guideline really is "all obstacles should be complex."

To counter the "all obstacles must be observed" crowd, I like to bring up the abatis. In lay man terms, an abatis is two trees blown down so they land obstructing the enemy’s direction of travel. Anyone traveling down the road will have to clear the fallen trees. Especially effective in heavily wooded forests, (think parts of Germany or the forests of Washington state) numerous abatis on an avenue of approach are a nightmare for an advancing force.

The abatis is a low tech solution (it was used to block carriages back in the day too) that still works to counter high tech modern armies. When combined with ambushes, IEDs and other unconventional tactics, the abatis can dramatically slow a conventional force. Most important, abatis don't need to be observed. Only a small number actually have to be watched to accomplish their mission. The abatis wears down the invader; combined with ambushes, they set his nerves on end.

In high intensity warfare, the minefield does not have to observed. Minefields terrify dismounted troops, with or without observation. Again, the best use of mines is when they can be observed. But if you have no choice and scatter a minefield without observation, they will still dramatically stall a units advance. Even if it is unobserved, a minefield will force a unit to clear the obstacle, and use a limited corridor through the minefield. And no matter how confident the engineers are that they cleared the minefield, the infantry guys will still be incredibly nervous.

The enemies of the US military, and Army in particular, will create obstacles in the future they do not cover with observation. These obstacles will still be effective, particularly in unconventional war. Commanders, if they are clever, should be prepared to lay obstacles even if they cannot observe them. We should remember the difference between guidelines and rules; fighting under too many rules erodes a commander's initiative, leadership, and creativity.

(By the way, check out Starbuck's thoughts on last week's post over at Wings Over Iraq. He emphasized the "canned" nature of too many training exercises. I couldn't agree more.)

eight comments

This whole series is about how rules are ridiculous, made to be broken as the saying goes.

I’m reading Blink right now, and one of the chapter sis about a Marine CO who defeats his opponents in a training exercise because he refuses to follow the rules.


Great overview of the subject of obstacles with insightful abstracts. The title was clever too. Nice work.


Yeah Eric you are referencing Paul Van Riper in the Millenium Challenge. He breaks some rules to win, the military doesn’t break some rules and loses, but neither side understood political war. Its a good example of how a creative enemy would devastate the US Army though.


Thoroughly enjoying your posts. With your discussion of rules and guidelines, you’ve hit a nerve. I believe that we throw out a lot of good guidance because it was not taught in an intelligent way. As I’ve stated before, I think the real issue is that doctrine is meant to be taught so it can be applied with judgment. WHY a certain guideline is in place must be central to this education. Only understanding WHY provides the basis for understanding WHY or WHY NOT in application. When it’s presented without context, there is little option but to either blindly accept it or reject it. I thought the following passage from a recent Australian Army Journal article (“”How Stupid Are We?” by LTC Richard King AUS Army: http://www.defence.gov.au/Army/lwsc/AAJ_.. ) was relevant and on point:
“The best we can achieve with doctrine is to ‘habitualise’ what we thought we had to do at a time in the past when we wrote the doctrine. Doctrine that takes years to review, produce and validate is out of date and representative of an outdated paradigm. All doctrine should be ‘developing doctrine’ and subject to continuous review and improvement. Currently, doctrine entrenches what we did do. We can only become adaptive if we encourage a focus on what we could do; but that would require creativity and innovation.”
With regards to your specific example. Obviously, a mine, or other obstacle covered with observation and fire is more effective in stopping an enemy. There is a dilemma created by a combined arms effect. However, is this the purpose of our adversaries? It seems obvious that they want to raise the cost, in terms of time, attrition and resources, for everything we do. Unobserved obstacles, such as IEDs are perfect for this purpose. They could throw in the odd complex ambush to keep us on our toes (which they do), but they get much more bang for the buck, with far less risk to their force, by simply employing IEDs alone.


Phil, I think you hit the nail on the head. If someone only knows the rules, without knowing why the rules exist, they are severely limited in their capability.

Again, I compare it to art. You need to learn why you follow the rules of art, then you can break them.


I’ll jump in here- I don’t think the problem is people blindly sticking with doctrine, I think it’s that people don’t know it. Many younger officers know little bits…(3:1 offensive ratio, obstacles needing to be observed…etc) but they look at these out of context and they almost become mantras. Michael asked me about this and I had to dig through my stack of field manuals to find the one on countermobility, luckily I’m a nerd, so I have things like that. In my short career, I haven’t seen doctrine taught. If anything it gets casually referenced – but never learned.

I blame it partially on the Center for Army Lessons Learned (CALL). They put out great publications, but they tend to be purely focused on tactics, techniques and procedures (TTPs). These are essentially tips on what works in certain situations. These TTPs have replaced doctrine instead of complementing it.

I love obstacles- I had an awesome time creating obstacles in training and then breaching them in Iraq.

Also- understanding doctrine gives you the base needed to be creative.


Jon, Fully agree—don’t tell me you’re “throwing out the book” or “thinking out of the box,” until you convince me you know and understand the book or box to begin with.


Jon great point about CALL being part of the problem. I couldn’t agree more that we focus way too much on simple, immediate solutions. I believe that ideas like 3:1 and all obstacles must be observed worked like that in the past.

Phil R, as for your point, I one hundred percent agree. Just too many people don’t understand doctrine, and TRADOC doesn’t help much either.