I can't find anything about this anywhere, but I was reading up on the famous Siege of Belgrade (at the time, called Nandorfejervar) in 1456, and the similarities of this bit of history to Tolkien's battle of Minas Tirith, struck me.
The similarities are both obvious and striking, starting with the name: Nandorfejervar means "Nandor's White Castle," and Minas Tirith is also called "The White City." It's a white castle on a hill, next to a river and surrounded by the city, with elaborate walls between each segment of the city.
Janos Hunyadi (Aragorn), king of Hungary (Gondor), learns that Turkey (Mordor) is planning a massive invasion of all of Europe (Middle-Earth), beginning with the closest major city, Nandorfejervar (Minas Tirith). So he goes across Europe gathering allies, and the Pope (Elrond) announces a crusade (quest) to repel the invaders.
Few nations (races) respond, and Hunyadi returns to Belgrade -- including by boat up the river with more reinforcements -- to find the massive Turk army having already encircled and invaded the city, though the castle in the center has not yet been breached. They attacked the much larger force from behind, and eventually drive them off.
Then Hunyadi contracted a disease from the Turk soldiers and died (married an elf).