For many years serious students of the First World War have lacked a detailed English-language guide to the French Army. Apart from the British guide to the French army that was published in 1914, no such guide has been produced. In this, the first of two volumes, the authors seek to fill this gap through the provision of detailed information on the infantry and cavalry divisions of the French Army. The French Army expanded from 43 active infantry divisions, and 10 cavalry divisions, in 1914 to a total of 140 divisions of infantry, and to 12 of either mounted or dismounted cavalry. The vast majority of these formations served on the Western Front in defense of France itself. Coverage includes a listing of those divisions of the Allied armies, British, American and Italian, serving under French command at various times. For each division, the authors provide a full listing of all the constituent components, whether they were infantry, artillery, cavalry or engineers. This will enable readers to reconstruct the composition of each division on any given date. In addition to a list of commanders, a detailed narrative of its operational history is provided. This full treatment of the divisions is complemented by a series of detailed lists of all the metropolitan and colonial regiments from which the divisions drew their manpower. These lists cover infantry, artillery, cavalry and engineers. The large number of regiments raised and employed operationally precludes coverage as detailed as that provided for the divisions, nevertheless, a much useful data is provided.