Battle Studies is a book by Ardant du Picq, a colonel in the French Army who was killed in 1870 in the Franco-Prussian War.
The theme of the book, according to Marshal of France Ferdinand Foch, is that "moral force" is the most powerful element in the strength of armies and the preponderating influence in the outcome of battles.
In general form, he states: Combat is the object, the cause of being, and the supreme manifestation of an army.
All the resources accumulated in time of peace, all the training, and all the strategic calculations must have the goal of combat.
Battle Studies became a key textbook in the French Army's École de Guerre in the years leading to World War I.