Note: This post and two others that follow will attempt to give some insight into the French use of blockhouses. Since I’m not an expert on the topic I won’t go too far into the weeds of the technical aspects of French defensive tactics (for fear of drowning) and also because this is a blog and not a book or scholarly article. The main purpose of this post is to provide some reference graphics to those who might be interested in the topic and/or for use in making war game terrain. There will be three .pdf downloads that will consolidate the many and various pictures I have on this subject. I’ll follow this post up with another that focuses on the blockhouses used in the First Indochina War 1945-1954 and another on the more familiar blockhouses found in North Africa.
INTRODUCTION: I’ve always been intrigued by the French Army’s employment of blockhouses in their various colonial adventures. They seem to have placed an inordinate trust in this tactic and the ability of these isolated small scale outposts (usually located within line of sight to each other) to provide security to the logistical road networks and populated areas and provide early warning and information of enemy movements and activities. A trust that lasted longer than those of other armies. Looking back in history, I’m not sure it worked quite as well as they thought it did, yet this tactic (first used in large numbers in colonial North America) became a trademark of French occupation tactics and colonial warfare. Blockhouses were built by Napoleon’s armies in Germany, Russia and Spain and would appear throughout Algeria starting with the French invasion of Algiers in 1830. Fortlets and blockhouses were built along major road networks during the Mexican debacle and then again in Madagascar, Dahomey and especially Indochina. These structures would proliferate throughout western Algeria along the indeterminate border with Morocco and later within Morocco itself. In the 1920’s, several dozen blockhouses were hastily built along the French defensive lines north of Fez during the Rif War. Many of these fell to Rif assaults and their garrisons were wiped out to a man.
After WWII the French in Indochina continued to rely on the vast existing network of these blockhouses and mini-forts in fighting against the Viet Minh and began to build more and more of these (of various construction) to better control pacified areas. Towards the latter years of that conflict the French doubled down on a major static defense plan for the north and created what was to be an interlocking belt of over 1,200 (900 were actually built) of these forts informally named the De Lattre Line. Many of the De Lattre fortifications were constructed to withstand heavy enemy fire and resembled concrete pillboxes.
Other countries used blockhouses too. Britain was successful using them to secure road and rail networks, bridges, garrisons and camps, and to cordon off large areas from Boer guerillas in South Africa. The Spanish had blockhouses throughout Cuba and the Philippines during their prolonged struggle against insurgents in both countries. These were somewhat effective as strong points against the Americans in 1898 outside of Santiago and Manila. The Spanish would also erect blockhouses along their defensive lines in northern Morocco at Cueta and Melilla.
My problem with blockhouses and other static defensive strong points is that they cede too much territory and maneuver space to the enemy and their garrisons become complacent and/or ineffective in their patrolling and offensive operations. They were often manned with ill trained local militia / security troops. Blockhouses may work well during the day in securing supply networks but at night individual forts quickly become targets of opportunity for an aggressive and agile enemy (that more often finds and exploits gaps between them vs. attacking them directly). In the Indochina War French blockhouses quite often became merely range markers for recoilless rifle and mortar teams and secondary targets attacked by the Viet Minh only to lure relief forces into ambushes. Blockhouses built by the French during that conflict would increasingly be made out of concrete and tied to other stronger supporting defenses. The De Lattre Line would group several of these towers and strong points into a cluster where all could be supported by a main base providing artillery support and quick reaction forces backed by armor. Nevertheless, many of these were simply low-hanging fruit for the communists.
There were many types of defensive structures used during the French occupation of Indochina. Major indigenous structures most often consisted of very large earthen mounds that formed a high wall around key towns, garrisons and royal palaces. Among these were the citadels at Hanoi (Thăng Long), Hue, Saigon, Lang Son, and Son Tay. Smaller populated areas and even villages had smaller versions of an earthen mound, sometimes topped by a bamboo wall, to protect it from the depredations of Chinese bandits (pirates known as the Black Flags). These perimeters would be surrounded by a palisade of bamboo poles and immense piles of cleared bush. Diagrams made by the French show that the infamous “punji-stick” traps were a common tactic well before the Americans showed up. The fortified towns would have one main entrance that would be closed and closely guarded at night. The road leading to this gate was often flanked by rice paddies for several hundred feet which severely limited the frontage of an attacking enemy.
Terrain also played a key roll in determining location of French bases. Commanding positions along major rivers were established and there are several pictures depicting garrisons perched on precipitous spurs and outcroppings. Blockhouses would often dominate the key terrain around French bases and were necessary for maintaining line of sight communications in the era before wireless.
The French, during the conquest of Tonkin, began to consolidate their gains by taking over existing fortresses and towns and then reinforcing them in a typical European fashion. Fields of fire were cleared, parapets reinforced, and artillery placements were surveyed and laid. Construction of numerous western style barracks, stores, stables and magazines were completed as well as building the inevitable blockhouses. These were built to provide the main defensive lines with a final fall back position–a fort within a fort. Outside the main bases blockhouses were also erected on hilltops for maximum observation as well as on defensible terrain that tied into securing the extended area. During the Siege of Tuyên Quang (Nov 1894-Mar 1895) the blockhouse established on the west side of the perimeter, until it was evacuated, served to foil several Chinese attempts on the outpost.
The early blockhouses erected in Indochina were larger and more commanding than those structures the French built there after WWII. Blockhouses were three or four stories high and rectangular in shape with an open air top floor covered by a thatch or tile roof. As mentioned their construction were often tied into an existing defensive perimeter and often functioned as a gate house at the main (and only) entrance into the garrison town. Eventually these blockhouses would be established along key lines of communication at 1 kilometer intervals and would be known as poste kilométrique.
NOTE: The first picture in this post is an amazing recreation of a French watchtower used for the 2002 film The Quiet American. (I found it at this page). It is well weathered with falling plaster so I thought it would be a good representation of one of the older blockhouses built before WWII. The Quiet American is a novel written by Graham Green in 1955. The story has a scene where the two protagonists get trapped in the tower by the Viet Minh. The book also mentions the Foreign Legion several times so I’ve added this to my read pile. The Quiet American was first made into a movie in 1958 but I have not been able to see if they had a similar watch tower made.