This work, the third in a four volume series, takes a fresh and in-depth look at the events of the opening months of the Franco-Prussian War between Napoleon’s Imperial Army and King Wilhelm’s German armies, when within the space of four weeks in the summer of 1870 the established order was overthrown and Prussia laid the foundations for a military and political hegemony in Europe which led directly or indirectly to two World Wars.In preparing this work the author has drawn heavily on the numerous volumes of the French official account, La Guerre de 1870–71 published by the Section historique de l’État-major de l’Armée around the turn of the 20th Century, which in addition to making use of information not available to the authors of the earlier German official history also includes detailed annexes providing copious orders of battle, after-action unit reports and casualty records for almost every engagement. This excellent source material has been supplemented by the works of Lehautcourt and the memoirs of many of the French commanders with additional detail and analysis derived from the numerous official and semi-official Staff studies published during the 1880–90’s. While many of the German works have been published in English few, if any, of the French works have been translated and their inclusion within this work will hopefully provide both a fresh perspective of events as well as providing a useful counterpoint to the somewhat ‘Prussian-centric’ viewpoints reflected in many previous works.Following on from the previous books in the series, the Opening Engagements and The Battles around Metz, the third volume take a fresh and detailed look at both the military and political background to this short but decisive campaign which saw French and German forces clash at Nouart, the encounter battle at Beaumont and the pivotal engagement of the campaign, fought between Marshal MacMahon’s Army of Châlons and the combined German armies under General Moltke outside the walls of Sedan.The detailed narrative is complemented by extensive orders of battle and casualty lists derived from the French and German official histories and is accompanied by a number of maps together with color and black and white illustrations.