Very interesting and insightful post! But what gives you the notion that "Tolkien was not writing political allegory" - if you throw in a bit of deeply-felt religion, that is precisely what he was writing.
Actually, Tolkien would tell you that.
Because Tolkien himself said so in the foreward to LOTR:
"As for any inner meaning or 'message', it has in the intention of the author none. It is neither allegorical nor topical. As the story grew it put down roots (into the past) and threw out unexpected branches: but its main theme was settled from the outset by the inevitable choice of the Ring as the link between it and The Hobbit. The crucial chapter, 'The Shadow of the Past', is one of the oldest parts of the tale. It was written long before the foreshadow of 1939 had yet become a threat of inevitable disaster, and from that point the story would have developed along essentially the same lines, if that disaster had been averted. Its sources are things long before in mind, or in some cases already written, and little or nothing in it was modified by the war that began in 1939 or its sequels."
Tolkein himself swore up and down that he never wrote the book as an allegory. He simply wanted to write a great story, with the pipedream hope that it might be considered the mythology of the UK, which, he claimed, missed out when the Normans squashed Anglo-Saxon culture on the island.
It was not allegory. Tolkien said so.
It was JUST a good story. Jeez...
Also, Orthanc was a dark tower, made of black stone, and Saruman originally was a good guy with the same charge to combat Sauron, but was turned to evil by the lure of the One Ring.
When Saruman realized that Sauron would probably acquire the ring first, then he allied himself with Sauron.
Tolkien was not writing "allegory", that is, he was not writing a fake "history" that paralleled what was going on in 1944 (he started writing it in 1938, and in 1944 was writing the Two Towers section of the novel).
However, he was writing imagined "history"...and did note that historical stories had APPLICABILITY to the present day world.
So anytime we confront evil, we see similarities. Islamofascism is no different from the evils of Naziism or communism: They seek to take over the world with power to remake simple human beings, and to replace God (Eru in the books) with themselves...there is no place in these utopias for simple hobbits who seek merely a normal family life and simple pleasures like beer and parties...
Ironically, Tolkien compared Saruman with the materialistic West, including the USA, which gloried in mechanics and industry but ignored nature and having fun (hobbits). That is why the "greens" love him...
I really think you have that backwards. No doubt their was some "political" allusion, but IMHO, it is a timeless Biblical good vs evil epic and very much in the the Catholic tradition --- evil is 100% evil yet seductive and powerful far beyond the ability of flawed humanity to resist. Only the most innocent, pure and humble spirit could possibly defeat the evil.
He was writing a myth, in which certain truths about human nature and human interaction are captured in a fictional setting which has no direct correspondence to any actual events.