Gentlemen,
In my experience a sword that will break when using the mune or shinogi to parry is an inferior blade. I have personally done extensive testing with Japanese and Japanese style swords. The martensitic edge is brittle, it will notch, chip, and possibly crack when struck with another sword of realitively comparable quality. The mune and shinogi of a properly forged sword will take considerable abuse without cracking or breaking. The edge of the attacking sword will usually cut into the mune and shinogi to some degree however there is not damage that would impair the function of the sword. To take a full cut from another swordsman without a parry of some kind is indicative of a serious mistake in the flow of combat. In my opinion using the edge to block is only done in a desperate circumstance. Even a parry with the blade at an acute angle to the cut will usually damage the edge to some degree. If you were in a situation, such as a battle, where the edge was used numerous times to block with the sword would suffer serious damage to the point where it's cutting ability would be compromised. Your training should entail protecting the asset that you are using to fight with. If you are a boxer it is your hands. Modern military it is your rifle. Ancient Samurai it was your sword. Proper training and ability should allow you to make minimal contact with an opponents sword when engaged. Proper parrying and passing with not only protect your sword but will significantly enhance your chance of victory.
James Williams
James Willliams
Kaicho
Nami ryu