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Natural Lines of Drift and the Least Effort Principle

Recently, a question was brought up regarding our (The CP Journal’s) use of “Natural Lines of Drift”. To be clear, when we discuss the domain, “Geographics”, identifying a natural line of drift is a key principle.  Understanding this principle can help us determine which route the enemy has used, the suspected route the enemy has used, or a predicted route the enemy will use. This is beneficial in finding our enemy, or anticipating methods and areas of attack.

I presented the picture (left) to another instructor, and said we would like our students to consider roads and trails to understand the terrain and how it is used. My fellow instructor responded, “If your topic ‘Natural Lines of Drift’, which is defined as a route one would most likely take and is usually associated with a path of least resistance, then the picture to the left is not a “Natural Line of Drift’, is it?”

He was right.

At first glance, it appears this route has violated the path of least resistance, therefore it is probably not a “Natural Line of Drift”, but rather a man-made path, or a road.

The path of least resistance or the principle of least effort is the path taken requiring the least effort.  I like to think of this as the path that water would take if it flowed downwards. Clearly, as one can see, it appears this road goes down, up and down again. If no roads existed, could you imagine taking the route in this photo?

If you look at the above photo again, could the road have been created to flow naturally with the terrain? If an individual were driving, it would make sense to use the routes designated.
If one were walking, however, human beings will utilize a path of least resistance.   Human beings will walk in curved lines, creating paths around obstacles.  We understand that the shortest distance between two points is a straight line, but human behavior shows that this is not always the case. Obstacles, terrain, and weather are important factors guiding human behavior.   As you look at the picture to the right, you will see that over time, even with a designated route, a path was created that fits natural human behavior.  Often times you will see individuals walking across streets, between bushes and over fences.

How many times have you found yourself cutting corners, and occasionally violating a designated pathway?

I was reminded that sometimes our simplest terminology could be subjected to a variety of factors.  It is our jobs as instructors to be clear in our definitions to cover everything we want Marines to consider.

When we discuss a “Natural Line of Drift” it is important to note that we consider all routes, pathways, roads, trails and human behavior.  In planning, one could observe a terrain map to determine likely avenues of march.  One could use satellite imagery to determine trails commonly used. Through sustained observation, one could identify routes taken, and anticipate routes taken in the future.  The tactical consideration is to apply the principle of least effort when observing routes. This will assist the trained observer in being able to detect patterns of human behavior.



  • Patrick Van Horne

    Good post, certainly a relevant discussion for Geographics. The Least Effort Principle requires careful consideration, especially when looking at the top picture. Ill refrain from going into mathematical definitions about work, but if the slope of that hill is very extreme, by extending the road a longer distance but with a more gradual incline, it could make the route “easier.” I was at a basketball stadium a couple weeks ago that was on top of a hill (Go ‘Cuse) and the walk ways that were laid out to get to the entrance were similar to the paved road. They had us winding our way up to the top of the hill, as opposed to taking the most direct route, which would have had us on our hands and knees. Often times in conditioning hikes, you will see Marines trying to weave their way to the top of a steep incline, because it feels easier, even though they go are travelling a longer distance.

    With the picture on the bottom being flat ground, the route that is put in place requires additional work because you have to go a longer distance, so why not cut the corner? It’s shorter.

    Perhaps something for discussion when we talk Natural Lines of Drift is observing “violations of existing pathways.” These deviations from the beaten path would also show a higher degree of familiarity with the environment, another important aspect of Geographics.

    This is open to anyone, not just Rick, but what are your thoughts on this? Do we need to redefine how we refer to Natural Lines of Drift?

    Again, great post.
    – Patrick

  • Christopher Cagle

    What is the seminal work on geographics that brings forward concepts such as the “least effort principle”? This makes me think of the history behind the free running/parkour craze – the idea of fleeing pursuit by the most direct, least effort, fastest route that is also nearly impossible to follow at the same speed if not trained in parkour (see chase scene in Casino Royale movie).

  • Rick Gonzalez
    Rick Gonzalez


    The principal of least effort, is the study from Dr. George Kingsley Zipf, in his 1949 publication, “Human behavior and the principle of least effort”. In it he discusses how human beings want the greatest outcome for the least amount of work.
    His work has been used to assist in formulas for criminologies geographic profiling.

    We take the concept and turn it on its head, can we predict how one would use their terrain using these concepts?

    Parkour is a phenomenal activity, and I am glad you mentioned it. Participants see it as a challenge to overcome obstacles… to find the fastest way over. Initially, the obstacle is NOT the economical choice, violating the natural lines of drift. However, over time, it is traversed with ease. Physically demanding at first, but over time, it becomes easy. The same applies for EVERY person, not just these physical phenoms. A wall requires scaling, and initially it is a mentally daunting task to figure a way over. A shopping cart is placed upside down and the wall is easily scaled. A demanding task at first, but over time, it becomes easy.

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