The treatment of the subject matter has remained the same throughout; it represents, as in the first edition, the principle that tactical lessons must be deduced from human nature, from the effect of weapons, and from experience in war, proper regard being had for national characteristics and historical transmission. _Tactics is psychology._ My statements in regard to fire effect are based, as before, upon the works of His Excellency, Lieutenant-General Rohne. The publications of Historical Section I of the Great General Staff and the splendid works of the late Major Kunz, furnish the basis for examples cited from military history. An almost too copious literature is already available on the Russo-Japanese war. The monographs (_Einzelschriften_) of the Great General Staff, and of Streffleur, especially “_Urteile und Beobachtungen von Mitkämpfern_,” published by the latter, afford a rich field for research. It is not difficult to cite examples from military history in support of any tactical procedure, but such examples require a very careful sifting before they can be recommended as worthy models for our action in front of the enemy. The Austrians deduced the necessity of the most brutal shock action from the experience gained by them in their combats in Upper Italy in 1859, and the British were not very far removed from completely denying the feasibility of making an attack soon after the Boer war; but the desire to avoid losses was forced into the background by the necessity of annihilating the enemy. In the Far East the Russians finally had to learn again the same bitter lessons as at Plevna. Simultaneously with this fourth edition, there appears in Athens a translation in Modern Greek from the pen of Captain Strategos of the Greek General Staff, well known to many German officers from his War Academy days. It is hoped that the fourth edition may receive the same kind reception at home and abroad that was given its three predecessors. For all communications, suggestions or corrections, directed either to me or to my publisher, I will be sincerely grateful. THE AUTHOR. POSEN, March, 1908. CONTENTS. =INTRODUCTION.= PAGE =1. War= 1 Eternal peace 1 War the _ultimo ratio_ of state policy 2 Courts of arbitration 3 =2. Strategy and Tactics= 4 Definition of strategy and tactics 4 Relation of strategy to tactics 6