Thank you both for replying, and I fully agree with 'so far as it goes' Burrahobbit. A work as wide-ranging and complicated as LOTR badly needed a coherent geo-political framework, and it's not surprising that, consciously or unconsciously, JRRT settled on one that so closely matches a historical situation from a period he happened to be a world authority on - so far, so obvious.
A good reason to set out these historical parallels is a continuing sadness (which JRRT surely shared) about how little people know of this history. If you don't know the events of Alfred the Great's reign, please, please do read up on them. This was a key turning point in not just English but world history, and it's also a great STORY. From the despair of defeat to the eventual recovery and victory is an emotional rollercoaster on a par with LOTR itself, and these things actually happened...
A related issue of great interest is the creative process which led to LOTR. Say you decided to write an epic fantasy saga. You want the prevailing mood to be one of a titanic clash of civilisations, with one side apparently doomed to inevitable destruction, and the annihilation of not just the people but their whole history and culture. How would you research the mindset of the outnumbered and threatened side?
From a European perspective you might start with writers from the end of the Western Roman Empire facing barbarian invasion, or perhaps the fall of Byzantium to the Ottoman Turks in 1453 (which incidently has strong parallels to the mood inside Minas Tirith during the siege). More recently, the impact of european colonial expansion on native cultures was just as catastrophic, but apart from Native American accounts there are few written sources (US readers might be somewhat surprised, not to say offended, to hear the rush to the Pacific Coast so described, but in world-historical terms that's exactly what it was). Finally, and in a category all of it's own (and not available to JRRT) is Holocaust Literature.
JRRT probably didn't do any overt research in this way, but then he didn't have to. Want to know what the end of the World feels like? Try reading the Anglo-Saxon Chronicles for the 860's and 870's. A lifetime of reading these accounts both professionally and for his own pleasure meant that they could hardly fail to permeate into JRRT's world view. This is the main reason for my view that LOTR could have been written at almost any time after the Victorian Era (when concerns about the effects of industrialisation and the mechanisation of the coutryside were already widely expressed) and the advent of WWII is irrelevant. At any time doesn't mean by anyone however - the perculiar nature of JRRT's genius is what keeps us all reading his astonishing books.
Finally, and in a Loki-like spirit of mischief, I can't resist pointing out the ultimate parallel between Alfredian history and LOTR.
The Ring: something taken into the heart of the enemy's camp, which effectively neutralises the threat from that enemy.
= Christianity itself. The conversion of the Danish commanders after Ashdown as a condition of the Peace Treaty removes the immediate threat to Wessex, allowing time for consolidation and recovery, whilst simultaneously undermining morale and coherence among the Danes.
No wonder Frodo is seen by so many commentators as a Christ-like figure. It's not the Ring he's taking into Mordor, but the Gospel itself, which he delivers to spectacular effect in his own Sermon on the Mount (Doom).
