Fortified Sector of Maubeuge The Fortified Sector of Maubeuge ( " Secteur Fortifié de Maubeuge " ) was the French military organization that in 1940 controlled the section of the Maginot Line between the French border with Belgium and Maubeuge , a distance of about . The sector was not as strongly defended as other sections of the Maginot Line Large portions of the Maubeuge sector were defended by blockhouses or casemates . The sector includes only four " ouvrages " of the type found in stronger sections of the Line , arranged in an arc to the north and east of the fortified city of Maubeuge , incorporating defenses from the First World War . The Maubeuge sector and the Fortified Sector of the Escaut were the final sections of the Maginot line to be authorized , and were termed the " New Fronts . " In the Battle of France the large fortifications of Maubeuge successfully resisted determined German bombardments and infantry attacks , despite their failure to protect Maubeuge against the Germans , who had outflanked the defensive line and who assaulted the fortification lines from the rear . Surrender or evacuation came only after the positions were surrounded and cut off from any hope of reinforcement . One " ouvrage " and one pre - Maginot fortification have been preserved . Concept and organization . Initial work in the sector established a series of casemates in the Mormal Forest , well to the rear of Maubeuge . The casemates were built by the " Commission d ' Organisation des Régions Fortifiées " ( CORF ) , the Maginot Line ' s design and construction agency . At the same time , studies proceeded on the fortification of the exposed salients , or " môles " of Bavai and Maubeuge . As the fortification of the Maubeuge Front was commenced later than the main section of the Line to the east , funds were restricted by the impact of the Great Depression , which had reached France . A relatively ambitious project was nevertheless advanced , planning for five artillery " ouvrages " ( Eth , Bavai , Quatre - Bras , L ' Épine and Boussois ) between Valenciennes and the Ardennes . The plan was progressively scaled back to four infantry " ouvrages " in front of Maubeuge , resembling larger - than - usual casemates more than the mutually - supporting artillery positions of the main Line . Sarts and Boussois , the last - surviving artillery " ouvrages " , were reduced to infantry positions . Geological and groundwater conditions made construction of deep " ouvrages " of the kind found in the main Line difficult in the Maubeuge area . The plan was also affected by political considerations , in which the fortification of the Belgian frontier was seen as a betrayal of the French plan for forward defense on Belgian territory . The CORF lines were augmented by lesser positions in the principle line of resistance constructed in 1937 - 38 , backed by further fortifications about to the rear , built in 1940 . A total of 300 fortifications were built to cover of frontier , but in 1940 there were only enough fortress troops to fully man the CORF positions and 125 of the hastily - built reinforcing positions . Command . The Maubeuge sector was under the overall command of the French 1st Army , under the command of General Blanchard , which was in turn part of Army Group 1 under General Gaston Billotte . From 16 March 1940 , the sector became the 101st Fortress Infantry Division . The SF Maubeuge was commanded by General Hanaut , then General Béjard from 1 January 1940 . The command post was at the Wargnories farm . Description . The sector included , in order from west to east , the following major fortified positions , together with the most significant casemates and infantry shelters in each sub - sector : In addition to the cancelled " ouvrages " mentioned below , the Ouvrage de Bavai was also planned for the sector , but never built . Sub - sector of Hainaut . 87th Fortress Infantry Regiment ( " 87e Régiment d ' Infanterie de Forteresse ( RIF ) " ) , Lt . Colonel Corbeil Resistance line ( FCR / RM ) : 105th CEO 104th CEO 103rd CEO Stop line ( FCR / STG / RM ) Reinforcing Line , Mormal Forest Sub - sector of Thièrache . 84th Fortress Infantry Regiment ( " 84e Régiment d ' Infanterie de Forteresse ( RIF ) " ) , Lt . Colonel Marchal 102nd CEO 101st CEO Second position History . Battle of France . On 16 May 1940 , elements of German Army Group A , including the German 8th and 28th Infantry Division s crossed the Belgian - French border , heading east along the frontier , directly for Maubeuge . Just to the south the German 5th and 7th Panzer Division s moved on a parallel line , along with the German 12th Infantry Division . The retreating French 1st and 9th Armies fell back to Maubeuge . The 28th ID and the 5th Panzer Division quickly moved against Maubeuge from the south , capturing the city ' s Vauban citadel on 17 – 18 May . Fort de Leveau to the northwest of Maubeuge fell on 18 May , a victim of German forces that had moved behind Maubeuge . By the 19th the German formations had rolled up the fortification lines along their path , and had encircled the remaining Maubeuge fortifications . Boussois , the easternmost " ouvrage " , came under attack on the 18th from the 28th ID and the 5th Panzer Division . As the day wore on , Ouvrage La Salmagne , Ouvrage Bersillies and Ouvrage Les Sarts all came under fire from the rear . Each position resisted fiercely , holding off the attack for several days , despite direct fire by German 8 . 8cm anti - tank guns that progressively reduced their ability to respond . Boussois and Les Sarts came under attack by Stuka s on 20 May . The Héronfontaine casemate came under sustained attack on 21 May , and a German 210mm mortar began firing on Boussois the same day . The bombardments continued , but were not able to bring about a surrender . Infantry assaults eventually reduced the positions one by one : Boussois at 1100 and La Salmagne at 2030 hours on 22 May , Bersillies at 1015 on 23 May with the nearby casemate Crèvecoeur , and finally Les Sarts at 1100 on 23 May . The garrison of casemate Héronfontaine held out until nightfall , when they were able to slip away . As the " ouvrages " came under attack , the surrounding blockhouses were being reduced one by one . The 5th Panzer Division moved into the Mormal Forest and cleared the defensive line there , where a major four - day battle had taken place between French and German mechanized forces . Despite the fierceness of the fighting around Maubeuge , casualties on both sides were light . The delay allowed a significant portion of the 84th RIF to escape to the Dunkirk pocket to be evacuated to England , while the 87th RIF escaped to Normandy to be captured weeks later . The Germans stripped the Maubeuge fortifications during the Occupation , removing weapons for re - use and salvaging the massive steel cloches for scrap . While Maginot fortifications in other sectors were restored for further use during the Cold War , the SF Maubeuge was not reactivated . Units . The 84th Fortress Infantry Regiment occupied the sub - sector of Thiérache , spending the winter of 1939 - 1940 building the Avesnes belt of light fortifications . The regiment ' s second and third battalions faced Rommel ' s 7th Panzer Division . As German forces reduced the defenses the individual battalions were compelled to retreat . The first battalion was captured at Blarégnies on 22 and 23 May . The remaining units made their way to Dunkerque where they were evacuated to England in the Dunkirk evacuation . Four years later the unit returned as part of the French 54th Infantry Regiment , which was captured by German forces in the Falaise area on 17 and 18 June 1944 . The 87th Fortress Infantry Regiment manned the Hainaut sub - sector . Attacked from 17 May , the regiment began to fall back to Erguennes on 20 May , while the fortified positions held out until 23 May . The first battalion was able to escape to Dunkerque and was evacuated . The unit formed part of the ill - fated 54th IR in Normandy , and was captured at Falaise . Present status . La Salmagne is managed by a preservation society and is occasionally open to the public . Fort de Leveau is preserved by the town of Feignies and its World War II era additions are preserved as well .