The well-known military critic and writer leaves the problem of disarmament aside and, in his usual brilliant style, attempts to get at rock-bottom considerations of modern warfare. Taking as his keynote the mobility of armies, the author starts out by demonstrating that in the last war armies had mass without velocity, with the result that there was a general paralysis in the form of trench warfare. Infantry tactics have obviously become impossible in the days of mechanization and cavalry of the old kind has also passed its usefulness. Military organization must therefore adapt itself to the demands of mechanization and the only solution lies in the development of large numbers of small fast tanks to take the place of cavalry and in the extension of the use of nonlethal gases, which, for effectiveness and humaneness, are preferable to almost all other modes of warfare. This general argument is set forth by the author with great conviction, the thesis being fortified throughout by reference to concrete problems, not only of the English and colonial forces, but also of the French and German armies.