In spring 2017 I spent one week in Northern France for learning French and for visiting historical sites in Lorraine and Alsace (Elsass-Lothringen) near the border to Germany and Luxembourg.
The entire border area from the Atlantic ocean to Switzerland was one (or the) main theater for war operations during the 1st and the 2nd World War, and so a lot of monuments or remains of fortifications like the Maginot Line can be found and visited in those former war zones.
La ligne Maginot
After their almost defeat in the 1st World War, French engineers devised a sophisticated system of concrete fortifications (la ligne Maginot) alongside the border to Germany between the wars, with building measures initiated in 1929.
The Maginot Line covered almost the entire border area, but had comparatively weak fortifications alongside the frontier to Belgium, especially in the Ardennes (Ardennen) where the Allies did not expect major offensive operations.
So the Line turned out to be utterly worthless as the German troops marched through Belgium and the Netherlands (by violating their neutrality) in 1940 and circumvented the strong points of the line.
The erection of this fortification system was one of the most useless engineering works in the 20th century and nothing but a waste of resources (similar to the German Atlantikwall).
The Ouvrage Hackenberg (ouvrage means “construction” or “work”) was one component of the Maginot Line, situated about thirty kilometers northeast of Metz, the largest city in Lorraine (Lothringen).
This fortification devoured enormous resources, and the irony was that parts of the fort were solely used by the Germans in an attempt to withstand American troops in late 1944.
I attended a guided tour through parts of the facility which are opened to the public. That included also a museum and small exhibitions about, for example, ammunition, weaponry and the logistics for the garrison.
The fort possesses several levels and extends over several kilometers, so visitors must be transported by an electric trolley through the tunnels of the ouvrage.
Interesting to see were the four souterrain diesel generators (which were still ready for operation as far as I remember) which ensured the power supply for the fort.
The fort is on the whole well-preserved since it was never involved in major defense battles.
The only exception was in 1944 (as mentioned) as the westwards positioned block 8 was utilized by the Wehrmacht against the advancing U.S. Army.
The used material for the bunker systems was reinforced concrete with a special concrete compound, which was very resistant against most kinds of shellfire.
1st World War fortifications
Unlike the 2nd World War, Lorraine was heavily devastated between 1914-18.
But the fortifications were the cardinal factor in the eventually successful defense battles of the French Army, hence catalyzing the notion of building an even stronger defense line to withstand future attacks.
But such fortification systems were not longer effective and outdated against the emerging mobile warfare twenty-five years later.