These attacks often occur at very close range and with little or no warning. Thus, the officer has little time to react. Each of the defensive systems is feasible under certain circumstances, but may have limitations that the officer or trainer should consider carefully. An attack with an edged weapon represents a deadly force threat to the police officer and is logically and legally countered with the same degree of force. Firearms are useful if the police officer can make use of cover, has a sufficient reactionary gap, or combines the use of a gun with physical defensive tactics. Grappling and pressure point systems specifically target the limb that is holding the weapon. Unlike these systems, the Modern Warrior system relies on scientific principles of body mechanics and focuses on targeting and controlling the assailant's entire body as a means to control the weapon. Trainers should constantly assess what is being taught and how it applies in the real world. Photographs