Fortified Sector of Altkirch The Fortified Sector of Altkirch ( " Secteur Fortifiée d ' Altkirch " ) was the French military organization that in 1940 controlled the section of the French frontier with Germany and Switzerland in the vicinity of Basel . The sector ' s principal defense against an advance from Germany was the Rhine itself , which could be crossed only by boat or by seizing a bridge crossing . The frontier with Switzerland was not regarded as a high - risk location , save for a possible advance by German forces through Switzerland . Originally planned as a full extension of the Maginot Line with artillery " ouvrages " , the sector ' s fortifications were scaled back and chiefly took the form of casemates and blockhouses . The SF Altkirch adjoined the Fortified Sector of Mulhouse to the north and the Fortified Sector of Montbéliard to the west . Concept and organization . The region bordering Switzerland was treated as a low - priority area , but received a substantial number of casemates and blockhouses nonetheless . Initial plans floated in 1934 proposed four artillery " ouvrages " at Stetten , Ranspach - le - Haut , Bettlach and Trois - Maisons , with four more infantry " ouvrages " at Uffheim , Helfrantzkirch , Ranspach - le - Haut , Bettlach and Oltingue . These were to be supported by 68 casemates . The project was cancelled in 1936 and were replaced by a more modest program that created three centers of resistance at Sierentz , Bettlach - Oltingue and at Roedersdorff - Blochmont . A total of six blockhouses were built , each housing two 75mm guns , with six more blockhouses armed with two 47mm guns , two machine guns and two automatic rifles . Three more resistance centers were proposed at Stetten , Ransbach - le - Haut and Trois - Maisons in 1937 , but were replaced by more casemates , prepared for mobile 155mm and 240mm howitzers to cover the bridges at Basel and Huningue . Thirteen blockhouses , four observation positions and fourteen infantry shelters were planned for the Glaserberg , along the Swiss border . Command . Until 16 March 1940 , the Altkirch sector was part of the Fortified Region of Belfort . Afterwards , the Altkirch sector was under the command of the 44th Army Fortress Corps under General Tence , which was in turn under the command of the French 8th Army , General Garchery at the Fort de Giromagny , part of Army Group 3 under General Besson . The 44th Corps ' headquarters was at Dannemarie . The 67th Infantry Division , commanded by General Boutignon , provided infantry support . The 67th DI was a series B reserve division , not suitable for heavy or sustained combat Following to its reorganization , the sector was called the Defensive Sector of Altkirch . The SF / SD Altkirch was commanded by General Salvan . Fortress troops were provided by the 12th and 171st Fortress Infantry Regiments . Artillery support was provided by the third and fourth battalions of the 159th Position Artillery Regiment . At the midpoint of the Battle of France on 1 June 1940 , the fortress troops of the SF Altkirch amounted to two fortress infantry regiments in five battalions , comprising 165 officers and 3 , 300 men . Description . The sector includes , in order from north to south , the following significant casemates and blockhouses in each sub - sector : Sub - sector of Franken . 171st Fortress Infantry Regiment ( " 171e Régiment d ' Infanterie de Forteresse ( RIF ) " ) , Lt . Colonel Demange . All positions were constructed by the Army Engineering Service " ( Service Technique du Génie ( STG ) ) " . < / div > Sub - sector of the Ill ( Durmenach ) . 12th Fortress Infantry Regiment ( " 12e Régiment d ' Infanterie de Forteresse ( RIF ) " ) , Lt . Colonel Françon . All positions were constructed by the STG . Four heavy gun emplacements were planned : < / div > Troop barracks were located at Uffheim , near Ranspach - le - Bas , near Bettlach , Ferrette and Raedersdorf . Glaserberg . Additionally , 47 positions were planned by the " Main d ' Oeuvre Militaire ( MOM ) ) " , which was in charge of small - scale fortifications , on the Glasenberg massif looking into Switzerland . 29 were built , a mixture of blockhouses , observation points and infantry shelters . Battle of France . The German offensive ( Operation " Kleiner Bär " ) across the Rhine was concentrated in the area near and to the north of Colmar , with little fighting in the Altkirch sector . The offensive , launched on 15 June , was rendered unimportant when the German XIX Corps under General Heinz Guderian reached the Swiss border on 17 June , behind the main French line . The 12th RIF was deployed on the heights of the Jura until 17 June , when it was called back to Belfort for the defense of the city . The second battalion was captured the next day , while the first battalion , retreating to Masevaux , was captured on the 19th at Chapelle - sous - Rougemont . The 171st RIF began a retreat toward the Dollar Valley and Masevaux on 18 June . Fighting ensued at Sentheim on the 19th , with Colonel Lavelle ' s detachment and the 21st battalion captured there . The remainder retreated to the Lauw - Mortzwiller area . The second and third battalions were captured at Masevaux , while the remainder of the regiment , now amounting to about one hundred men , retreated through the Stiftkopf forest , ending up at the Tête - de - Neuf - Bois . On the 26th the regiment was ordered to the Charbonniers village , where it was captured .