May-June 1940. An unfortunate battle lost in forty-five days. A lot has been said about these forty-five days, whether through general works covering all or part of the period or monographs relating particular aspects of the battle. However, never has a book dealt with the whole day-to-day fighting, sector by sector, from Holland to Menton, with as much precision. Forty-five days of fighting are reported here, including the most emblematic, but also those more numerous and previously ignored, that have emerged from oblivion. The book covers the daily drama of the men who are overtaken by the rhythm of the battle, subject to the whim of the command, and many of whom were at the end of their sacrifice, which these two volumes propose to retell. This book offers a different and completely new vision of this battle. For more than 40 years, Jean-Yves Mary has been passionate about the events of May-June 1940. He became one of the specialists of the Maginot Line thanks to several references and the realization of the Maginot Line Museum and intervals at the Fermont site. He has studied carefully the various breakthroughs made by the Germans during these two tragic months, which resulted in the publication of several well-documented works on the Panzer division's stunning progression. A sum of knowledge gathered over the years has prompted the author to tackle this ambitious project. Text in French.