Monday 6 March 2023

The Battle of the Hedgerows - an example of rapidly-evolving bottom-up knowledge

The story of the "Battle of the Bocage" is a great example of evolving knowledge, driven from the bottom up.

Normandy Bocage
Image from
wikimedia commons
I am reprising this post from the archive, not just because its a great story, but because in demonstrates the maturing of knowledge through several stages, as described in this post from 2 weeks ago.  Thanks to Jack Whalen for first pointing me at this excellent Learning Story from WW2 and the D Day landings. 

What has been quoted as being "one of the greatest intelligence failures of all time", was the failure of the US forces to realise the nature of the battle they would fight after the D day landings - a battle in a maze of small fields, sunken lanes and almost impenetrable hedgerows, known as the Bocage.

For many of us brought up in rural Europe, where small fields and ancient hedgerows are a familiar site, we might have realised that this sort of landscape would be an obstacle. Yet for the US forces in early June 1944, the nature of the landscape was a huge surprise.  Hedgerows cultivated for over a thousand years to keep even the strongest bull in a small field, are not a feature of the American countryside. They are impenetrable to troops, and the earth banks under the hedgerow make them a death trap for tanks, as the unarmoured base of the tank is exposed as it climbs over. 

As one U.S. Army Captain put it, “We had been neither informed of them or trained to overcome them”. General Bradley called the Bocage the "damndest country I've seen."

Actually there had been warning of the hedgerows - see this quote from Brigadier General James M. Gavin- "Although there had been some talk in the U.K. before D-Day about the hedgerows, none of us had really appreciated how difficult they would turn out to be."  This is a classic failure of Learning Before - failure to share a context. The British would have known about the challenge of the hedgerows, as similar countryside is found in Devon, Dorset and south Somerset. They would probably have assumed that Americans knew about the challenge as well (this assumption is known as the Curse of Knowledge). The conversation might have gone

  • Brit "Watch out for the hedgerows"
  • American "Yeah no problem"

Whereas the conversations needed to have been

  • Brit, "No, I mean REALLY watch out for the hedgerows"
  • American "How do you mean? What's the problem with a hedgerow? Its just a few bushes, right?"
  • Brit, "Let me explain ....."

The Germans knew all about hedgerow warfare, and had been practicing tactics for months - tactics of covering fire, pre-aimed mortars, communication lines between fields, covering fire from parallel hedgerows, turning each field into a deathtrap. They knew that they were perfectly hidden behind the dense hedges. The Germans had a knowledge advantage; they had knowledge of "how to fight effectively in the Bocage", which the American troops did not have. 

As a result, the first few weeks were a nightmare for the American troops, losing on average one man for every metre of progress. Imagine marching down the road shown in the picture above, with the potential machine-guns behind every hedge.

However, despite this failure to "learn before", some very smart "learning during" went on to fill the knowledge gap. The Americans improvised and innovated in the early stages of knowledge development, with successful innovations including;
  • The Rhino Tank invented by Sergeant Culin - a tank-bulldozer combination, where recycled beach defences were welded to a tank, enabling it to burst through a hedgerow;
  • A communication system, where an infantry observer could shelter under or behind a tank and direct its fire, linked by telephone to the tank crew;
  • Use of light rifles for covering fire, instead of more unwieldy machine guns;
  • A whole language of hand signals for communicating between tanks;
  • Using the back of a tank as a platform for the mortar spotter;
  • Employing light aircraft to scout in advance.

The book "Busting the Bocage" summarises the learning approach (my emphasis in bold)
Ideas on how to achieve better results against the Germans came from a wide variety of sources. In general, ideas flowed upward from the men actually engaged in battle and were then either approved or rejected by higher commanders. Within the bottom ranks of the Army, individual soldiers suggested ways that enabled their units to move against the enemy. Sergeant Culin's hedgerow cutter is the best example of a single soldier's idea that influenced all of First Army. At the top end of the chain of command, general officers also produced ideas on how to defeat the Germans. General Cota's supervision of the development of hedgerow tactics in the 29th Division typifies the contributions made by general officers. 
The effort to gather ideas on how to beat the Germans was decentralized. There was almost no effort to work out an Armywide solution to the tactical problems of combat in the Bocage. The First Army staff made no distinct attempt to devise tactical solutions for. the whole command to use in overcoming the German defenses. First Army did publish and distribute to all units a series of "Battle Experiences," reports that contained information and lessons learned in battle. The bulletins were not directive in nature, but subordinate commanders were expected to use the information to assist them in finding ways to defeat the Germans. In fact, in only one area did First Army headquarters take an active role in dealing with tactical problems: the production and distribution of Sergeant Culin's hedgerow cutter.

What explains the decentralized, collective method of tactical problem solving exhibited within First Army? Firstly, the U.S. Army was not in a position to analyze the German defense systematically and produce one best solution for attacking through the hedgerows. First Army simply did not have the time to slow the pace of combat operations while seeking a uniform, coordinated solution to tactical problems. The U.S. Army had to push inland and expand its beachhead as a prelude to larger operations. Corps and division commanders received orders and were expected to execute them as quickly as possible while overcoming all difficulties. Commanders who did not perform well were relieved; several division commanders lost their posts during the Normandy campaign.
Once the knowledge of tactics had been created, it was rapidly spread among the various divisions through use of the bulletins. Individual divisions created their own variants of these approaches, which were shared as Example Practices.

Within a few weeks a standard practice was developed; a doctrine, or series of approaches, for clearing a field, involving the close operation of a tank and an infantry squad ("'One Squad, one tank, one field'"). This close operation of armour and infantry at this level of detail (single squad, single tank) was itself an innovation. 
As quoted here
"After the rehearsal on 24 June, the 29th Division's operations staff prepared diagrams and explanatory notes outlining the new hedgerow tactics in detail. The operations section then distributed the information as a training memorandum to all regiments within the division. Units in the 29th Division practiced and rehearsed the new tactics in preparation for their next bout with the Germans.  On 1 July, General Cota summed up the 29th Division's tactical experience in France: "What held us up at first was that we originally were organized to assault the beach, suffered a lot of casualties among key men, then hit another kind of warfare for which we were not organized. We had to assemble replacements and reorganize. Now we have had time to reorganize and give this warfare some thought. I think we will go next time"

Using the new knowledge, and with Rhin Tanks being manufactured in advance, the 2nd Battalion made spectacular progress. They completely ruptured the main line of German resistance.  Infantry casualties were relatively light during the attack, and not one tank was lost. Other US Army units delivered equally impressive advances.

Thus newly developed knowledge turned the tide of the battle.

This is an interesting story, and an interesting example of Learning in Action, when speed of deployment was more important than consistency. It is also an example of the development of knowledge, starting with the recognition of a knowledge gap, the bottom-up development within the community of practice of good practices, and the eventual development and application of a standard practice. 

Of course, were the context to change, the knowledge would need to go through a new cycle of development. Who knows how the tactics would change with the introduction of drones, satellite imaging etc. However within one month in 1944, the US Army was able to create, develop and deploy knowledge of a critical topic - "How to effectively fight your way through the Bocage".

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