In his book, the author shows the need for a detailed study of the enemy, the organization of systematic obtaining information about the enemy, attentive and impartial assessment and use. The author resolves the assigned tasks using concrete examples of the armies that participated in the world war of 1914-1918, and on the materials of the intelligence department of the General Staff of the American army. The book was published in Washington in 1936, and published just before the war in the USSR.