Which set of famous medieval events is Lord of the Rings based on? As I was under the impression it was pure fantasy - and if anything real world influenced the trilogy, its the horrors of the 2 world wars, and the Orcs may not be who most assume them to be, if you view them that way
Cal, Theoden's charge to break the siege of Minas Tirith is obviously inspired by Jon Sobieski's relief of Vienna (the largest documented cavalry charge in European history). And to even get that far, Theoden needed Ghan-buri-ghan's assistance... Athealtes at Thermopylae?
Speaking of Thermopylae, how about Hurin and Huor's stand at the Pass of Sirion at the end of the Nirnaeth Arnoediad? Leonidas all over again.
Tolkien also mentioned Boromir's (and Faramir's) heroic defense of the bridge at Osgiliath... taken straight from the legendary/historical feat of Horatius Cocles.
I'd also say that the Northern Numenoreans, i.e. the Lost Realm of Arnor, the former Kingdom of Arthedain, and the Rangers of the North mirror Israel. Just as the ancient Kingdom of Israel split along familial, tribal, and religious lines into Israel and Judah, Arnor split into Arthedain, Cardolan, and Rhudaur. Just as the Mesopotamian states of Assyria and Babylon overran Israel and Judah, Angmar consecutively conquered Rhudaur, Cardolan, and Arthedain. Just as the people of Israel were dispossed of their land for over two thousand years, the Dunedain (Numenoreans) of Arnor were dispossed of their land for over a thousand years.
The Numenorean settlement of Gondor (Numenorean upper class ruling over the men of Middle-earth) could be comparable to the Norman nobility ruling the Anglo-Saxon/Norse/Britons. The Gondorian Civil War could be compared to the Anarchy, the War of the Roses or the ECW. Eldacar, the restored son of King Valacar, was not of pure Numenorean blood.... Norman intermarriage with the Saxons.... or Scots.
Is the Gondor-Rohan alliance inspired by the Auld Alliance? Or is it more similar to Jon Sobieski's alliace with the Germans?
To me, King Arvedui's drowning in the Ice Bay of Forochel harkens to the loss of the White Ship.
I remember reading a comment by George R.R. Martin... he said that he is diligent to not copy any fictional literature, but that history was more than fair game for inspiration and retelling.