"It isn't more effective the well-armed soldier, but the soldier who is best prepared". With this premise, Master Isidro deals with an unresolved matter for professionals in the armies: working with combat knife. We will study the main principles, the aims, the most common mistakes, the ways to cut, and the techniques applied to each of the modes of combat such as knife against knife, left-handed opponents, smooth cuts, empty-hand techniques against knife, bayonet and firearms, subduing the guard and bow and crossbow exhibitions. A work that breaks with everything which was established in hand-to-hand combat techniques with the so-called silent weapons.