Why is a full tang sword important?
If a sword is not full tang, you should better not purchase it. Or you should not care about quality and safety. It does not really matter for a wallhanger or decorative sword. You can easily hang it on the wall, but do not remove it for use.
But why is this so important now?
Under the handle is a part of the blade with a sword, you don't see this immediately. The part of the blade under the handle, which you also call Nakago (with a Japanese samurai sword) or angel. In essence, with a full tang sword, this is the part of the blade that you hold in your hand and the entire handle is built around it. The tang is completely in the handle, that is the meaning of a full-tang sword. This applies to both Japanese katanas, Chinese swords and European swords.
A full tang means that the sword is forged from one piece of steel and that it is properly and tightly secured in the handle. So what's under or actually in the handle is the same piece of steel as the blade or blade you see. So the tang in the handle may not be welded, glued or screwed to the blade. Because if it does not consist of one part, then the chance is very, but also very large that if something is hit, the sword breaks in two. The consequences of this cannot be foreseen and are therefore extremely dangerous.
If you were to use a sword that is not full tang, but with half a tang for example, the balance of such a sword is also dramatic. You can't go completely blind about whether or not a sword is full tang. There are more aspects involved, you can only chop and cut with a full tang if the blade is made of a High Carbon Steel and has had a good heat treatment.
And as with everything else you can use the term full-tang sword inappropriately, sometimes you can also use this term in a somewhat nuanced way. Certainly on the internet sellers call everything without even realizing what a term means exactly. And in the sword world this certainly includes "battle ready" and "full tang".
It should not be that the part of the blade is so thin that it still does not give much strength to the blade in the handle. A forge with enough experience that aims to make a functional sword will include this in its design and production. I will make that clear on the basis of a sword design.
At A you see a full tang sword which is designed with a view to a functional sword.
At B you see a full tang but this will still not give sufficient strength, then the design is not correct.
So you have to see a term full tang in the entire design of the entire sword, then it has value. It must also be designed for functional use and that implies more than a full tang sword. A good hand forged high carbon steel blade with heat treatment is just as important. As well as a high-quality handle with a high mounting quality.
For a functional handmade sword, it is therefore best to choose an experienced forge. These are, for example, the Hanwei Forge by Paul Chen and John Lee. These also do a good quality check so that you are sure of a safe purchase.
Example of full-tang samurai sword by Paul Chen (Hanwei Forge)