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 a picture 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.