I told them that the Katana was the king of swords and that the Japanese made the best swords in the world (when the world was making swords). In comparison, the Europeans made better armour. This is a simplistic view. But it was understandable by 10 and 12 year olds.
This kind of thinking does get me wondering. Because at the end of the day, regardless of geography, we humans have the same physical architecture: two hands, two feet, eyes in an exposed head, and so on. So surely combative techniques, quite apart from metalurgic skill, should produce some similarities regardless of what part of the world the technique originated.
The difficulty is in selecting the period of time for the comparison, I think. If you look date for date in the East and the West you can get some quite bizarre results. During the 30 Years War and the English Civil War, for example (1618 – 1648), Europe was busily superceding the sword altogther and developing combined arms doctrine focussed on the gun (the result of which was the development of the Rapier for dueling which has a totally different design criteria than a sword designed for the rigours of pitched battle). In Japan it was a period of stabilisation and suppression of the gun, bringing the sword to an almost fossilised prominence. And sadly this is the time that is most often compared, inappropriately, because the Rapier and the Katana have nothing in common.
During the Eurpoean ‘Dark’ and Medieval periods history records the dominance of the one-handed sword and shield. One-handed fits with China and the Jian, but the shield? Certainly not in Japan.
But in between these times, around 1400 to 1500 or the European high Renaissance, I think there are great similarities. Armour was being reduced or eliminated. Guns were gaining dominance but were still slow to load. The sword in both East and West was still weapon of choice. The fact that none of the European techniques exist outside of manuals, in comparison to several Japanese techniques which have unbroken teaching links to the original, should not fool us into thinking that only the Japanese knew how to use swords and all that happened in the West was thuggish bludgeoning.
Claymores, Greatswords and Zweihänder have obvious similarities to Nodachis and it would be astounding if the methods to wield them were much different. But these were unusual, localised, weapons. The Bastard sword is the obvious candidate, but the very hand-and-a-half notion implies a transitional weapon: one that still allows old fashioned shield use.
Then I found it: the Kriegmesser. I have no proof yet, but I reckon that the original training and use of this sword would be recognisable to a practitioner of Japanese swordsmanship.
But as I say, I have no proof. History is largely silent on the Kriegmesser. But the history I can read is in English and English sources are perhaps understandably biased towards English experiences. Perhaps the German sources would tell me more.