Impact weapon attacks can come in many forms — baton, hammer, crowbar, or any number of weapon-like objects. Impact weapons (along with edged weapons) are often referred to in krav maga parlance as “cold weapons.” Attacks can come from a myriad of directions, heights, and angles in single-swing attacks. The three fundamental principles of defense are either (1) to close the distance between you and the assailant while deflecting-redirecting the attack, (2) to disengage until you recognize the correct timing to then close the distance, or (3) to retreat straight away.
Close the distance. The end of the weapon generates the most force, as the assailant’s wrist is used as a fulcrum. Therefore, the most dangerous range of the attack is to be struck with the very end of the weapon. In other words, the object’s momentum decreases the closer you come to the assailant’s swinging wrist. That’s why it’s vital to close the distance between you and your attacker as quickly as possible. Optimally, the distance between the defender and the assailant can be closed before a weapon is deployed while debilitating the adversary with strong combatives, blocking access to the weapon, and achieving dominant control. If the weapon is successfully deployed and put into action, closing the distance will allow the defender to either deflect-redirect or block the weapon, the majority of the time in combination with body defenses, while delivering withering counterattacks. As with all krav maga defenses, the hand always leads the body to deflect-redirect in conjunction with simultaneous multiple counterattacks.
Time correctly. Another essential to a successful defense is precise timing; closing the distance and using the correct tactic at the correct time. Fight timing is best thought of as the fusion of instinct with simultaneous decision making to either pre-empt the attack, move off the line of attack/fire, deflect-redirect, control the weapon and strike, or retreat from harm’s way. In other words, fight timing is harnessing instinctive body movements while seizing or creating opportunities to defend both efficiently and intelligently. Defined yet another way, fight timing is your ability to capitalize on a window of opportunity offered by your opponent or to create your own opportunity to end the confrontation using whatever tactics come instinctively to you. In short, you’ll attack the attacker. Importantly, the tactics and techniques are designed to provide the defender with a pre-emption capability prior to a weapon being deployed. The goal is not to allow an assailant to get the drop on you. Your recognition of his intent and body language literally and figuratively will allow you to cut the legs out from under him.
Retreat straight away. As soon as you see that the threat has been neutralized, retreat as soon as possible to avoid future attacks.
Source: http://www.artofmanliness.com/2013/08/22/krav-maga-technique-of-the-month-overhand-direct-one-handed-strike-defense/