For a long time I hesitated to comply with my publisher’s wishes for a new edition. It would not have been difficult to publish long ago a new edition, based upon the many lessons of war communicated to me by members of foreign armies soon after the Russo-Japanese war. But, after an extended period of theoretical work, I was more inclined to avail myself once more of the opportunity of gaining practical experience by service with troops. Pure theoretical reflection is only too apt to depart from the requirements of practice and to overlook the friction appearing everywhere. The battalion commander, more than any one else, is called upon to act as the tactical instructor of his officers and knows best where the shoe pinches. Moreover, the proximity of the maneuver ground to my present station gave me an opportunity of observing the field training of a large number of battalions and regiments of infantry and artillery, and to compare notes with brother officers of the other arms. In addition, several trips abroad and, incidental thereto, visits to battlefields, furnished valuable suggestions. I postponed issuing the new edition until the publication of the new Russian and Japanese Drill Regulations, which, with our own excellent regulations, best illustrate the lessons learned from the war in the Far East. For this fourth edition I was further able to draw upon the new French (1904), Italian (1905), Belgian (1906), U. S. (1904), British (1905), and Swiss (1908) Drill Regulations. This enumeration alone justifies the statement, “completely revised,” appearing on the title page. I have earnestly endeavored to make use of foreign experiences in detail. The words of Lieutenant-General Sir Ian Hamilton of the British Army, to whose writings I owe a great deal, deserve special attention in studying the drill regulations of foreign armies: “It is a blessing that the greater and prouder an army, the more immovably it is steeped in conservatism, so that as a whole it is finally incapable of assimilating the lessons gained by other armies. Military attachés may discover the most important points in the training and employment of foreign armies and urgently recommend their imitation, but their comrades will pay no more attention to them than did Napoleon III. to Stoffel’s reports on the Prussian army before the outbreak of the Franco-German war.”