Fortified Sector of the Sarre The Fortified Sector of the Sarre ( " Secteur Fortifié de la Sarre " ) was the French military organization that in 1940 controlled the section of the Maginot Line on either side of the Sarre river . The sector ' s defenses relied primarily on a system of inundations that could be created by fortified dikes and regulating weirs , backed by blockhouses . Weakly defended compared with other sections of the Maginot Line , the sector received a measure of attention and funding from the mid - 1930s when the formerly demilitarized Saarland was reintegrated into Germany . However , with a single " petit ouvrage " it remained a weak point in the Line . In 1940 the Sarre sector was attacked by German forces in the Battle of France . The inundations were only partly successful , and German forces were able to pierce the Maginot Line at the Sarre , allowing German divisions to move behind the main French line . Concept and organization . Compared with much of the French border with Germany and Luxembourg , the valley of the Sarre was not heavily fortified . As long as the Saarland was demilitarized , the sector did not face a significant military threat . With the union of the Saarland with Germany in 1935 , the area posed a greater threat . The shallow water tables in the area prevented deeply buried fortifications of the Maginot type in most of the sector , but presented opportunities for the defensive use of inundations . A system of reservoirs feeding diked impoundments gave France the ability to rapidly flood the valleys of the Nied and Moderbach rivers . The necessary dams , weirs and dikes were defended by blockhouses , and were themselves strongly built . The weakness of the western portion of the sector was cause for concern during the Phoney War of 1939 - 40 , resulting in the construction of the CEZF Line ( " Commission d ' Étude des Zones Fortifiées " ) , or Second Position , to the rear of the four western sub - sectors . A number of blockhouses were built under the auspices of the " Service Technique du Génie " ( STG ) , but the line was incomplete in 1940 , with long gaps between blockhouses . The " Région Fortifiée de la Sarre " ( " Fortified Region of the Sarre " ) was briefly created , encompassing the SF Sarre and the neighboring Fortified Sector of Rohrbach . The region existed for two months , in September and October 1939 . Several transfers took place of sub - sectors to and from the neighboring SF Rohrbach and SF Faulquemont . In particular , Ouvrage Haut - Poirier was attached to Rohrbach at the time of its construction . Until 15 March 1940 the sector was called the " Secteur Défensif de la Sarre " . Command . The Sarre sector was under the overall command of the French 4th Army , headquartered at Vic - sur - Seille , under the command of General Réquin , which was in turn part of Army Group 2 under General André - Gaston Prételat . The SF Sarre was commanded by General Boucher until 2 January 1940 , then Colonel Dagnan . The command post was at Hellimer . 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 20th Corps ( " 20e Corps d ' Armee " ) , General Hubert , commander . The 20th Corps was in turn made up of the 11th and 52nd Infantry Divisions , as well as the 82nd African Infantry Division Artillery support for the sector was provided by the 66th Position Artillery Regiment ( " Régiment d ' Artillerie de Position ( RAP ) " ) , which controlled both fixed and mobile artillery , commanded by Lieutenant Colonel Robert . The 11th ID and the 82nd DIA were made up of active - service troops , while the 52nd ID was a Class B reserve formation , not suitable for heavy or sustained combat . At the midpoint of the Battle of France on 1 June 1940 , the fortress troops of the SF Sarre amounted to two fortress infantry regiments in six battalions and two fortress machine gun infantry regiments in six battalions , comprising 600 officers and 17 , 000 men . After 13 June , many retreating units were organized into mobile units to try to establish stop lines . In the Sarre sector , retreating units were organized into the " Dagnan " group , under the 20th Army Corps ' command . Description . The sector includes , 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 Lixing . 69th Fortress Machine - gun Infantry Regiment ( " 69 Régiment des Mitrailleurs d ' Infanterie de Forteresse ( RMIF ) " ) , Lt . Colonel Jobin , command post at the Bois de Brill The sector included ten blockhouses , designated by number , and two artillery casemates , Noonenwald ( AC7B ) and Biding Nord ( AC 3B ) , which provided flanking fire along the blockhouse line with 75mm guns . The sub - sector ' s positions were located on the south bank of the Nied . Peacetime barracks and support : Sub - sector of Altrippe or Leyviller . 82nd Fortress Infantry Regiment ( " 82 Régiment d ' Infanterie de Forteresse ( RIF ) " ) , Lt . Colonel Matheu , command post to the south of the Vieux - Bois at Leyviller The sector comprised six blockhouses on the south bank of the Nied , with two flanking casemates mounting 75mm guns . The casemates were Biding Sud ( AC 5B ) and La Costaude ( AC 1B ) . Peacetime barracks and support : Sub - sector of Saint - Jean - Rohrbach . 174th Fortress Machine - gun Infantry Regiment ( " 174 Régiment des Mitrailleurs d ' Infanterie de Forteresse ( RMIF ) " ) , Lt . Colonel Duparant , command post at the Corne du Plaffenbusch The sector comprised ten blockhouses , mostly on the south side of the Moderbach , all built by the STG . The sector also included four fortified dikes intended to control inundations along the Moderbach : Water features included : Peacetime barracks and support : Sub - sector of Kappelkinger . 41st Colonial Machine - gun Infantry Regiment ( " 41 Régiment des Mitrailleurs d ' Infanterie du Casemate ( RMIC ) " ) , Lt . Colonel Tristani The sector lacked blockhouses or casemates entirely , consisting of two advanced posts , Grundviller and Hill 242 . Water features included : Peacetime barracks and support : Sub - sector of Sarralbe . 51st Colonial Machine - gun Infantry Regiment ( " 51 Régiment des Mitrailleurs d ' Infanterie du Casemate ( RMIC ) " ) , Lt . Colonel Revier de Mauny , command post at Keskastel Like the Kappelkinger sub - sector , the Sarralbe sub - sector had only two advanced posts : Willerwald and Kisswald . Peacetime barracks and support : Sub - sector of Kalhausen . 133rd Fortress Infantry Regiment ( " 133 Régiment d ' Infanterie de Forteresse ( RIF ) " ) , Colonel Bertrand , command post at Kalhausen Second position - CEZF Line . A fallback line behind the main line , roughly following the south bank of the Albe river . Twenty - two STG - style casemates were proposed , of which thirteen were constructed . History . Battle of France . The SF Sarre first saw action on 15 May 1940 , when German forces launched a brief offensive in the area , intended as a feint to draw French forces from other sectors , in particular from the area of Sedan , where the main German attack was to fall . Named Operation " Fackel " ( " Torch " ) , the German operation used three divisions , the 60th , 75th , and the 258th infantry divisions under the XII " armeekorps " . The operation was a success , surprising the French 11th Infantry and the 82nd Algerian Infantry divisions after a short but heavy artillery barrage . Initial German objectives were taken , but forces rallied and fought on for as many as three days . The French 2ndArmy Group withdrew to the vicinity of the Maginot Line and deferred transfers of forces to other sectors , achieving the effect desired by the Germans of preventing reinforcement at Sedan . The assault in earnest on the SF Sarre , Operation Tiger , opened on 14 June with an artillery bombardment that had little effect on French defenses . Nevertheless , the German offensive arrayed the German First Army ( AOK 1 ) , which deployed the XII ( XII AK , 75th and 268th IDs ) , XXIV ( XXIV AK , 60th and 252nd IDs ) and XXX ( XXX AK , 79th , 93rd and 258th IDs ) Corps , backed by a reserve composed of the 168th , 197th , 198th and 257th IDs against the French 20th Corps . The 20th Corps was composed of five regiments of fortress infantry supported by the 52nd ID and the 1st Polish Grenadiers . German air support was provided by V " Fliegerkorps " . The principal attack started at 0730 , with XII AK and XXX AK moving against the west side of the Sarre valley , XXIV moving to the east in support . The German attack focused on the Valette village . The attack met with mixed success , taking casualties from unsuppressed French artillery , but capturing several French blockhouses . The 93rd ID ' s attack stalled , however , taking fire from the main line of fortifications , forcing a withdrawal . An attempted crossing of the Nied by the 258th ID failed as well . Fire from a French 75mm casemate destroyed German artillery and bridging equipment . The 268th ID ' s attack initially stalled , but broke through French lines at Hoste . The 75th ID ' s attack across the Moderbach also produced success after an initial setback . XXIV AK ' s attack on the east side of the sector failed entirely and was the object of a successful French counterattack . Faced with the progressive collapse of the French First Army to the west , the French command in mid - June ordered the withdrawal of field army units and interval troops from the Maginot Line , to be carried out from 13 June . Operation Tiger therefore unfolded at the time of the planned withdrawal . With high casualties and less than overwhelming success , the commanding German Colonel General von Witzleben considered calling off the offensive , but a captured copy of French withdrawal plans caused him to continue the attack . That night French units moved south past the CEZF Line . The next day German forces pushed aside the French rear - guard and fought the French 52nd ID and the Polish Grenadiers , who stopped the German advance for the day and withdrew the night of the 15th . Serious French resistance to the German breakthrough ended , leaving German forces free to move along the Maginot Line ' s rear . The 262nd ID approached Haut - Poirier from the rear on 21 June . The Germans opened fire with 155mm artillery at 1500 hours , concentrating on Block 3 . Without artillery support from a " gros ouvrage " , and with Blocks 1 and 2 were unable to intervene , their fire blocked by terrain , Haut - Poirier surrendered at 2200 hours . The casemates nearby surrendered at the same time . After the June 1940 armistice the Germans stripped Haut - Poirier of all equipment . The " ouvrage " was in poor condition after the war and was not chosen for renovation . Units . The 41st Colonial Machine Gun Infantry Regiment defended the Moderbach and Albe valleys in the Kappelkinger sub - sector . In June 1940 the retreating 41st RMIC was attached to the " Dagnan " group of mobile forces and tretreated into the Vosges , fighting at Mittersheim , Avricourt and finally Nompatelize , where the unit surrendered to German forces on 22 June . The 51st Colonial Machine Gun Infantry Regiment was positioned in the Sarralbe sub - sector . It joined the " Dagnan " group on 14 June , retreating through Harskirchen to the Marne - Rhine Canal , then to Montreux , Neufmaisons and La Salle , surrendering near Rambervillers on 23 June . The 69th Fortress Machine Gun Infantry Regiment occupied the Lixing sub - sector , which was transferred to the SF Faulquemont on 15 March 1940 . During Operation Tiger , the regiment faced the German 258th Infantry Division . In retreat , the unit was attached to the " Girval " group as it made its way to the Marne - Rhine Canal from 14 June . The regiment was captured 19 – 20 June in the area of Lunéville . The 82nd Fortress Machine Gun Infantry Regiment was located in the Leyviller sub - sector . On 15 March 1940 the sub - sector fell under the control of the SF Faulquemont . Following the 2 June attack , the regiment retreated as part of the " Girval " group of mobile units , retreating in good order , but was taken prisoner between 19 and 21 June near Bruyères and the Col du Haut - Jacques . The 133rd Fortress Infantry Regiment was stationed in the Kalhausen sub - sector , which was transferred from the SF Rohrbach to the SF Sarre on 15 March 1940 . The regiment ' s second battalion provided the garrison for Ouvrage Haut - Poirier . Units of the regiment that could disengage retreated towards Sarre - Union and Fénétrange , regrouping on the Marne - Rhine Canal . Driven off the canal line , retreat continued to Raon - l ' Etape , where the unit surrendered on 21 June . The untis left at Haut - Poirier surrendered the same day . The 174th Fortress Machine Gun Infantry Regiment watched the Saint - Jean - Rohrbach sub - sector . Unusually for a fortress unit , the regiment took part in a brief offensive on the Wandt from 10 to 23 September 1939 , part of the " Marion " group of forces . The 174th ' s sub - sector was attacked by the German 52nd Infantry Division on 5 June , and was the object of a major thrust of Operation Tiger on 14 June . In retreat , the regiment was assigned to the " Dagnan " group , retreating to Salles . Present status . Haut - Poirier is on private property and is sealed to access . The Casemate de Wittring is maintained as a museum and may be visited . At Barst , two STG casemates have been restored as part of a display on the frontier defenses .