Thanks for those links,
SKB.
Needless to say, I am aware of the existence of Hatsumi-san but I did not know about his receipt of that award from the Japanese government. It surprised me a little as there is some controversy that surrounds certain published works from the esteemed gentleman, with regard to their historical accuracy. I'm guessing that the Japanese considered the positive aspects of his 'evangalism' of ninjutsu to outweigh the negative.
That documentary DVD looks enticing too - I don't know if it'll have me nodding my head or grinding my teeth but it's got to be worth a look

.
I get the feeling that we're talking at slight cross purposes in our discussion here. We actually fundamentally believe the same things I reckon, the difference being that my claim is that there was no actual, seperate, 'caste' of Ninja.
There were samurai who trained in these skills (the 'real' ones not the Hollywood smoke-bomb-and-black-mask tripe) more deeply than others but it was expected as part of a samurai's service to his lord that he would be willing to commit acts of espionage, theft or assassination as and when ordered.
Note that Japanese hstory is a notoriously difficult subject to study in as when a dominant family took over the temporary reins of power they tended to erase the written accounts of their predecessors and replace them with their own versions.
What has happened with the cult of the Ninja is that some 'scholar' (and I use the term loosely) fastened on the legends of the Ninja that inhabit the fiction of the period. This 'find' has been amplified beyond all reason by modern media to the extent now that it is almost impossible to have a reasonable discussion on the subject - people take what they see in films and fictional works to be some semblance of the truth and the much blander actuality of the history can't hold a candle to that

.
If you're generally interested in the history of Japan, have a browse around these sites to get a sense of where to direct your research:
http://www.samurai-archives.com/
http://www.sengokudaimyo.com/
Ooops, the missus is calling me to breakfast - I'll finish this up later ... back now, satisfyingly full of hot bacon and tomato sandwiches :yum:.
As to the Japancast post I referred to earlier, I can't find it either :blush: - no matter, the core of it was the same as what you yourself were saying i.e. that legends tend to have their roots in something real.
For example, Robin Hood may not have been as depicted in the story but the tale grew from a seed that was planted by the actions of a real man.
The same with the Ninja. What has passed into modern folklore bears no resemblance to what actually went on all those centuries ago but
something laid the groundwork for the tales that were written that were themselves scooped up and glamourised by later generations.
To round this off, you pose the perfectly reasonable argument that without any actual
acts that could be ascribed to Ninja, the use of their supposed existence as a propganda tool would soon lose it's teeth.
I concur and it's one reason why I keep going on about how there were actually no such thing as a specialised Ninja caste. In all the sources I've encountered, I've only ever found one incident that was specifically attributed to a 'Ninja' (this is the famous 'spear up the bum' assassination) - even there, it was also stated that the assassin was an enlisted ashigaru in the oppossing forces.
What kept the value of the myth alive is that assassination, theft and espionage by samurai were all too real in these centuries well before the much vaunted (but largely ignored) code of Bushido supposedly made such acts impossible for them. I like to think of Ninja as being more of a synonym for
agent than anything else i.e. a soldier employed in his daimyo's service being tasked with duties outside of the everyday.
Ooops (again) - this post is not having much luck today ... I've got to get ready for iai. Hopefully I've made some sort of sense, anyhow. I'm not putting this forward in an "I'm right and you're wrong!" fashion by the way. I'm genuinely looking for an open sharing of ideas and sources.