Fortified Sector of Montmédy The Fortified Sector of Montmédy ( " Secteur Fortifié de Montmédy " ) was the French military organization that in 1940 controlled the section of the Maginot Line between Sedan and Longuyon , a distance of about . The sector sector was not as strongly defended as other sections of the Maginot Line , facing the southern Ardennes region of Belgium . Large portions of the Montmédy sector were defended by fortified houses , blockhouses , or casemates . The sector includes only four " ouvrages " of the type found in stronger sections of the Line . The weakly defended area in front of Sedan was the scene of a major breakthrough by German forces in the opening of the Battle of France . This was followed by a German assault on the Maginot Ouvrage La Ferté , which killed the entire garrison , the only such event on the Maginot Line . Concept and organization . The sector was created in 1940 as part of the reorganization of the Meuse Front , which was combined with the Maginot Montmédy Bridgehead ( " Tête du Pont de Montmédy " ) and the Defensive Sector of Marville , itself separated from the Fortified Sector of the Crusnes . As a result , the fortifications in the new sector represent a wide variety of types and degrees of fortification . The Sedan sub - sector comprises two distinct lines , with fortified houses close to the border and a line of blockhouses along the line of the Meuse . The houses were built in 1938 by the Military Works organization ( " Main d ' Ouevre Militaire ( MOM ) " ) , while the blockhouses were built primarily by the Army Engineer Service ( " Service Technique du Génie ( STG ) " ) , beginning in 1936 . The Mouzon sub - sector was organized similarly . A number of blockhouses were built to local designs , such as the FCR or Billotte blocks of the Sedan sub - sector . The fortified houses took the form of a blockhouse on the ground floor with a light residential superstructure providing living quarters for the crew manning the blockhouse . Their armament consisted principally of light arms fired from a number of firing ports and embrasures , augmented by light anti - tank weapons . Fortified houses were sited close to the frontier , typically in a location that commanded the cross - border road . Blockhouses were plain concrete structures , providing little to nothing in the way of living quarters for their crews . Blockhouses typically displayed the rounded edges and shielded firing positions characteristic of artillery casemates and combat blocks of the Maginot " ouvrages " built by CORF ( " Commission d ' Organisation des Régions Fortifiées " ) , the Maginot Line ' s design and construction agency , but were usually built under non - CORF direction . Casemates tended to be built by CORF as part of the integrated Maginot defenses , and frequently mounted heavier weapons , of up to 75mm caliber . Both casemates and blockhouses could have infantry cloches or cupolas for observation and protected small - arms fire . Yet another organization was the Commission of Study for Fortified Zones ( " Commission d ' Études des Zones Fortifiées ( CEZF ) " ) , which planned and built blockhouses along the valley of the Meuse and the Chiers in the Sedan and Mouzon sub - sectors in 1940 , known as the Second Position . Command . The Montmédy sector was under the overall command of the French 2nd Army , under the command of General Charles Huntziger , which was in turn part of Army Group 2 under General André - Gaston Prételat . The SF Montmédy was commanded by General Burtaire , then General Renondeau from 27 May 1940 . The command post was at the Château de Tenay at Tilleuls . The interval troops , the army formations that were to provide the mobile defense for the sector , to support and be supported by the fixed defenses , were under the command of the 10th Corps ( " 10e Corps d ' Armee " ) , General Grandsart , commander , and the 18th Corps ( " 18e Corps d ' Armee " ) , General Rochard , commander . The 10th Corps was in turn made up of the 55th Infantry Division and the 3rd North African Division ( " 3e Division d ' Infanterie Nord - Africaine ( DINA ) " ) . The 18th Corps was composed of the 41st Infantry Division and the 3rd Colonial Division ( " 3e Division d ' Infanterie Coloniale ( DIC ) " ) . Artillery support for the sector was provided by the 1st Regiment of the 169th Position Artillery Regiment ( " Régiment d ' Artillerie de Position ( RAP ) " ) , which controlled both fixed and mobile artillery , commanded by Chef d ' Escadron Perry . The 41st ID and 3rd DIC were made up of Class A reservists , while the 55th ID was a Class B reserve formation , not considered suitable for significant combat . The 3rd DINA was an active - duty formation . At the midpoint of the Battle of France on 1 June 1940 , the fortress troops of the SF Montmédy amounted to four fortress infantry regiments in 13 battalions . 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 : Sub - sector of Sedan . 147th Fortress Infantry Regiment ( " 147e Régiment d ' Infanterie de Forteresse ( RIF ) " ) , Colonel Pinard , with the 55th DI as interval troops The Sedan sub - sector was not considered part of the Maginot fortifications , as they were built by organizations other than CORF and were planned as largely local initiatives , rather than as an integrated chain of advanced , mutually supportive fortifications . Line of fortified houses ( MOM ) , 1938 : Principal line of resistance ( FCR / STG ) , 1936 : 58 infantry shelters or " abris " , 1936 - 1939 . Additionally , a series of 11 Bilotte - style blockhouses were built as the " Second Position " stop line behind Sedan Sub - sector of Mouzon . 136th Fortress Infantry Regiment ( " 136e Régiment d ' Infanterie de Forteresse ( RIF ) " ) , Lt . Colonel Vinson , with the 3rd DINA as interval troops The Mouzon sub - sector was not considered part of the Maginot fortifications . However , a " gros ouvrage " was originally proposed for the sub - sector , the Ouvrage de Vaux - les - Mouzon . Line of fortified houses ( MOM ) , 1938 : Principal line of resistance ( FCR / STG ) , Chiers line , 1936 - 1940 : 104 infantry shelters or " abris " , 1936 - 1939 . Second Lines : A " stop line with 11 Bilotte - style blockhouses were built as the " Second Position " or " Meuse barrier " behind Charleville . A similar group of 14 " abris " formed the Meuse line / CEZF Line behind Montmédy . Sub - sector of the Tête de la Pont de Montmédy ( Montmédy Bridgehead ) . 155th Fortress Infantry Regiment ( " 155e Régiment d ' Infanterie de Forteresse ( RIF ) " ) , Lt . Colonel Culot , with the 3rd DIC as interval troops Second line : Nine blockhouses ( FCR / STG ) and two casemates , the Casemate de la Laiterie and the Casemate de Villecloye to the rear of the Maginot Line . The casemates each mounted a single 75mm gun . " ouvrages . Peacetime barracks and support : Sub - sector of Marville . 132nd Fortress Infantry Regiment ( " 132e Régiment d ' Infanterie de Forteresse ( RIF ) " ) , Lt . Colonel Blanchet , with the 41st DI as interval troops , command post at Grand - Failly . The Marville sector was a separate sector , the Defensive Sector of Marville , until March 1940 . History . Battle of France . On 13 May 1940 , the German Army Group A attacked the French 2nd Army in the vicinity of Sedan and Monthermé . The attack came as a surprise to the French forces of the Sedan sub - sector . The French 55th Infantry Division , a second - line reserve formation , had spent most of its time constructing blockhouses along the line of the Meuse and Chiers rivers , with priority going to the Chiers line . When the German attack came , it found the 55th ID unprepared for combat , and its blockhouses along the Meuse , the focus of German attack , were incomplete and unarmed . The attack by the German 1st , 2nd and 10th Panzer Divisions was preceded by a heavy aerial bombardment , which , while ineffective at causing casualties or damage to fortifications , effectively destroyed the division ' s will to resist . German infantry advances late on the 13th produced a disorganized retreat , and by the 14th the Germans had broken through the French defenses . As the French forces in the Sedan sub - sector fled , the Chiers line in the Mouzon sub - sector was exposed . Ordered by General Huntziger to retreat to new positions farther south , the end of the Montmédy Bridgehead became exposed . This was composed of the village of Villy , occupied by the 3rd Colonial Infantry Division , backed up by Ouvrage La Ferté , the effective western end of the Maginot Line . The Germans immediately moved to attack La Ferté ( known to the Germans as Panzerwerke 505 ) with the 71st Infantry Division . La Ferté , as part of the Maginot Line , was designed to be supported by its neighbors when under attack . Lacking a neighbor to the west , it had to depend on Ouvrage Chesnois for artillery support . However , the Maginot fortifications in the area were farther apart than in other sectors , and La Ferté was at the limiot of Chesnois ' artillery range . La Ferté was itself lightly armed , although it had been augmented with two artillery casemates armed with 75mm guns . These casemates , however , were not connected as part of the position ' s integrated defenses , lacking a secure underground connection to the main position . By 15 May the Germans were preparing an attack on Villy and La Ferté . On the 17th the Germans seized Hills 226 and 311 , which commanded the " ouvrage " and were used as firing positions for artillery . The Villy artillery casemates were evacuated by the French the same day . On the 18th Villy village was occupied by the Germans , despite determined French resistance from a series of fortified houses in the village . La Ferté was encircled . On 18 May the Germans moved closer to the " ouvrage " , employing direct fire with four 88mm guns . The exposed cloches and turrets became untenable , severely reducing the " ouvrage ' s " ability to resist the assault . A French counterattack failed . With the upper levels of both blocks on fire , resistance ceased on the 19th . Germans with respirators entered on the 20th and determined that the garrison was dead , killed by carbon monoxide poisoning . In June the remaining garrisons of the " Tête de Pont de Montmédy " were ordered to withdraw the night of 10 – 11 June to straighten French lines , and to avoid La Ferté ' s fate . The fortifications ' arms and infrastructure were sabotaged before they were abandoned . Evacuation was complete by 12 June , a day ahead of the scheduled withdrawal , which resuled in the uncovering of the west flank of Ouvrage Ferme Chappy to the east . The German 169th Infantry Division advanced to take possession of the salient on 13 June 1940 . The Germans stripped the Montmédy 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 Montmédy was not reactivated . Units . The 132nd Fortress Infantry Regiment was shifted from the SF Crusnes to the SF Montmédy on 16 March 1940 , holding the Chiers line . As part of a general withdrawal of French fortress inits from the Maginot Line , the 132nd RIF pulled back on 13 June and joined the " Division de marche Burtaire " , retreating to Verdun . The regiment was assigned to hold the Fort Douaumont on 14 May . On the 15th the regiment was ordered to continue retreating in the direction of Toul . It was eventually captured to the south of Toul in the area of Colombey - les - Belles and Goviller between 20 and 22 June . The 136th Fortress Infantry Regiment covered the Mouzon sub - sector . The sector came under air attack from 10 May 1940 , with infantry attack from 12 May . On the 14th the regiment moved back to the Inor belt of fortifications . On 21 May the 6th company was captured by German forces in the Hache forest and the Inor line was abandoned , falling back to Stenay . As the unit fell back it organized anti - tank barricades along the route . The 9th company was captured at Azannes on 14 June . The 136th was at Crepey on June 25 for the armistice . The 147th Fortress Infantry Regiment was stationed on the Sedan sub - sector . The regiment came under attack from 13 May and was pushed back to the Fort du Rozelier nea r Verdun by 21 May , when it was attached to the 71st Infantry Division , which became the 17trh ID two days later . Reorganized as the 59th Light Infantry Regiment on 5 June , the regiment fall back to Arc - en - Barrois . The 155th Fortress Infantry Regiment held the Tête du Pont de Montmédy , the most exposed portion of the sector , including La Ferté . The regiment was engaged from 13 May , and retreating to the Inor area after the loss of the La Ferté and its garrison on 19 May . The units sabotaged their positions and retreated on 12 June . They were attached to the ; " division de marche Burtaire " , falling back to the Verdun and Saint - Mihiel area . After briefly freeing gironville , the regiment was captured 20 – 22 June near Toul . Present status . La Ferté is a French war memorial , with a small cemetery nearby . The other three " ouvrages " are abandoned although the surface of Vélosnes is maintained as a nature trail ; its interior is a protected refuge for bats . Casemates and blockhouses may still be found throughout the sector , but none are specifically protected or restored .