This was a German offensive by Generaloberst Erwin von Witzleben’s 1st Army and Generaloberst Friedrich Dollmann’s 7th Army of Generaloberst Wilhelm Ritter von Leeb’s Heeresgruppe 'C' against the French Maginot Line defences in Alsace (15/25 June 1940).
The French defences were those of the southern part of Général d’Armée André Gaston Prételat’s 2e Groupe d’Armées (one British and 35 French divisions in all) and the whole of Général d’Armée Antoine Marie Benoit Besson’s 3e Groupe d’Armées (10e, 7e and 6e Armées with 14 French divisions).
The 1st Army advanced through the line on a southerly axis from the area around Saarbrücken with subsidiary advances moving to the west in the direction of Metz and to the south-east in the direction of Strasbourg, and the 7th Army on a westerly axis from the area around Freiburg. The German offensive eventually surrounded the remnants of the 2e Groupe d’Armées in an area bounded by Mulhouse, Epinal and Belfort, where they surrendered as the Franco-Axis armistice came into effect.
At this time large portions of the Maginot Line defences were still in French hands but, because of their very nature, impotent to affect the course of events.