Editing Maginot Line (section)

==== Features ====
[[File:Fort Saint-Gobain p1410129.jpg|thumb|{{convert|81|mm|in|abbr=on}} [[mortar (weapon)|mortar]]]]
The specification of the defences was very high, with extensive and interconnected [[bunker]] complexes for thousands of men; there were 45 main [[fort]]s (''grands ouvrages'') at intervals of {{convert|15|km|mi|abbr=on}}, 97 smaller forts (''petits ouvrages'') and 352 [[casemates]] between, with over {{convert|100|km|mi|abbr=on}} of [[tunnel]]s. Artillery was coordinated with protective measures to ensure that one fort could support the next in line by bombarding it directly without harm. The largest guns were, therefore {{convert|135|mm|in|abbr=on}} fortress guns; larger weapons were to be part of the mobile forces and were to be deployed behind the lines.

The fortifications did not extend through the Ardennes Forest (which was believed to be impenetrable by Commander-in-Chief [[Maurice Gamelin]]) or along France's border with Belgium because the two countries had signed an alliance in 1920, by which the French army would operate in Belgium if the German forces invaded. However, after France had failed to counter the [[Remilitarization of the Rhineland|German remilitarisation of the Rhineland]], Belgium—thinking that France was not a reliable ally—abrogated the treaty in 1936 and declared [[Neutral country|neutrality]]. France quickly extended the Maginot Line along the Franco-Belgian border, but not to the standard of the rest of the line. As the [[water table]] in this region is high, there was the danger of underground passages getting flooded, which the line designers knew would be difficult and expensive to overcome.

In 1939 [[United States Army|U.S. Army]] officer [[Kenneth Nichols]] visited the [[Metz]] sector, where he was impressed by the formidable formations which he thought the Germans would have to outflank by driving through Belgium. In discussion with General Brousseau, the commander of the [[Metz]] sector and other officers, the general outlined the French problem in extending the line to the sea in that placing the line along the Belgian-German border required the agreement of Belgium, but putting the line along the French-Belgian border relinquished Belgium to the Germans. Another complication was Holland, and the various governments never resolved their problems.{{sfn|Nichols|1987|p=27}}

[[File:Fort Saint-Gobain p1410059.jpg|thumb|Corridor inside the Fort Saint-Gobain near [[Modane]] in the [[Alps]]. The [[Decauville]]]]
When the [[British Expeditionary Force (World War II)|British Expeditionary Force]] landed in France in September 1939, they and the French reinforced and extended the Maginot line to the sea in a flurry of construction from 1939 to 1940, accompanied by general improvements all along the line. The final line was strongest around the industrial regions of [[Metz]], [[Lauter (Rhine)|Lauter]] and [[Alsace]], while other areas were, in comparison, only weakly guarded. In contrast, the propaganda about the line made it appear far greater a construction than it was; illustrations showed multiple storeys of interwoven passages and even underground [[rail yard]]s and [[Movie theater|cinemas]]. This reassured allied civilians.