The realm just to the north of Gondor. It is known as the ‘Kingdom of The Horsemen’ for its famous cavalry. The flag of Rohan, home to The Rohirrim.
Rohan becomes an important ally of Gondor due to their invaluable cavalry support first in the Battle of Hornburg against the Wizard Saruman (not to be confused with the far worse Dark Lord Sauron.) Then the climatic Battle of Pelennor Fields where the Rohirrim are led into battle against the forces of Mordor by their King Theoden.
In one of the best and most exciting moments in The Lord Of The Rings, Theoden’s niece, Eowyn, kills the leader of the Ringwraiths and kills the the horrifying Nazgul. No one could do what this young woman did.
In Tolkien’s story the Nazgul is definitely pterodactylic. At one time Gandalf referred to them as ‘Nazgul-birds’. There is some ideas that Tolkien took the idea from an insect.