NOTE: This is the second part of my take on French blockhouses. It utilizes two primary sources: Rand Memorandum 5271-PR A Translation From the French: Lessons of the War in Indochina VOL 2 (page 116 “Fortifications”) and an online version of a book called La Guerre D’Indochine by Maurice de Poitevin (Chapter VII, The War of the Posts).
After the Japanese surrender in 1945, when the French moved swiftly to regain control of their far-flung colonial possessions, we see an almost immediate resurgence of guerilla warfare in Indochina. By 1948 the level of Viet Minh insurgent activity is rapidly escalating and for the first time the tactic of watch towers and blockhouses becomes central to the French strategy in controlling their so called “pacified” areas. Promoted by General De La Tour, this tactic was started in the south (Cochinchina) and later utilized in Annam (the center of modern Vietnam) by 1950.
“The watch towers were field works manned by several men (five to six auxiliaries) established along the length of a road (generally within sight of one another, and at an interval of approximately 1 km) in order to:
- Prevent the cutting of the road, protect local facilities, observe movements, and insure free access
- Assist vehicles and contribute to their protection in case of attack
Certain towers, called “mother towers,” were provided with larger forces and increased fire power, in the case of an ambush on a convoy, personnel from these positions sounded the alarm and halted all traffic while mobile elements from specified military posts quickly moved into the area. This procedure yielded excellent results at the beginning, but it quickly became ineffective.
From 1950 on the Viet Minh in Central Vietnam began using shaped-charge projectiles fired from weapons delivered to them by China. Masonry was unable to stand up under such fire, and the small garrisons of these field works would often avoid sounding the alarm, preferring to abandon their position rather than to expose themselves to certain destruction.
Another limiting factor of the “poste kilométrique” tactic is that it did not work in the stronghold areas of the Viet Minh which were the heavily forested northern and western highlands that run along the border of Laos and Cambodia and China to the north. Here the French had limited visibility along their lines of communication so watch towers were ineffective. The French had to establish much larger bases and launch mobile operations against their elusive enemy.
Starting late 1950 the French began a serious effort in the north to protect the Red River Delta region from encroaching Communist efforts. A fortification line extending south from Tien Yen in the extreme north and that curved west to encircle Hanoi and then back east to the coast was built. This was nicknamed The De Lattre Line, after General Jean de Lattre de Tassigny, and consisted of a line of concrete fortifications (towers, pillboxes, bunkers) obstacles, and weapons installations constructed to guard the essential lines of communication between the cities of Hanoi and Haiphong and to provide security for the densely populated and economically important Delta area against attacks by both the Viet Minh and any potential invasion from Communist China. The De Lattre fortifications more often resembled the reinforced concrete pillboxes and bunkers used by the German along their defensive lines on the Western Front in WWII.
The De Lattre Line was to comprise 1200 separate concrete blockhouses able to withstand 155mm artillery. They were grouped in 250 clusters of 3-6 blockhouses for mutual fire support over a span of 235 miles (378 km). Each blockhouse was to hold a minimum of 10 men. In addition a defensive redoubt was to be constructed around a 22 miles (35 km) radius from the port of Haiphong ensuring its safety from artillery attack. All these new defensive lines were to be connected by roads capable of bearing 30-ton tanks. Construction commenced in late 1950 and was mostly complete (913 fortifications) by the end of 1953. The picture below shows one of the types of bases that would have several towers in the immediate sector that it would be responsible for manning and for relief if attacked.
Ultimately the fate of French Indochina would be determined by the French defeat at Dien Bien Phu in 1954 and the towers and blockhouses that dotted the entire region had little to no effect on this final act of a 67 year drama.
Here are the pictures I’ve collected on this topic. These were literally collected from a multitude of various places on the internet over the course of several years and it would be impossible to go back and provide attribution and I apologize for not annotating them properly or giving credit to any original content. I hope that this post makes up for my lack of courtesy regarding the images. The images were cropped in two MS Powerpoint presentations (one in landscape and the other portrait). They were joined in Adobe PDF.