Internal vs. External Energy

The question of internal vs. external is a common one in the martial arts world.  There is only internal energy.  What is commonly called external energy is simply force, which is never ever the proper response to any attack.  The proper response is to direct the energy used in the attack back into the attacker.  You use your opponent's limbs as weapons against him or her.  This can only be done if the defender assumes an oblique angle against the attacker and issues the response to the attack in an arc rather than a straight line.  This is why in the Celtic systems, arm strikes are delivered from the opposite shoulder and leg strikes are delivered from the opposite hip.  The strike is delivered in such a way that the striking limb of the defender deflects the opponent's strike while simultaneously delivering the defender's own strike into the opponent.  As in all the Celtic systems, the response comes from the use of the sword.  In sword play, the goal is to cut without being cut; to strike without being struck.  This is the same goal as all other martial arts.  It does you no good to deliver a blow and to suffer a blow; to simply trade blows.  That's external and it's frankly stupid.  By delivering a strike from the opposite side of the body of the limb being utilized to deliver the strike, the body must turn; the torso must twist.  This turning and this twisting is what gives power to the strike.  It also moves one's torso out of the way of the opponent's strike, thereby allowing the opponent's striking limb to bypass the defender's torso.  The defender's torso has evaded the opponent's strike.  That's the internal power and it's the only kind of power that ought to be used in any combative situation.  That's the reason power in the Celtic Systems resides in the knees and elbows.  Even though the strikes are mainly delivered with the forearms and the shins, the forearm is used as an extension of the elbow, while the shin is used as an extension of the knee.   The strikes are windmill strikes, with the axis at the elbow and the knee and the blade at the forearm and shin.