After the Return of The King Aragorn Elf-Stone to the throne of Gondor and Arnor at the end of the Third Age of Middle-Earth, the Fourth Age was a peaceful and prosperous one. King Aragorn and the Elvenqueen Arwen Evenstar ruled from the White City of Minas Tirith, and bounty flowed from the lands of men. In Rohan, the Horselords of the Rohirim led by Eomer renewed the Oath of Eorl, binding the two kingdoms of Western Men together in friendship. After Aragorn's passing, his son Eldarion took the throne, and continues to rule to this day. King Eomer, lacking in the graceful long-life of the line of Numenor, passed his throne to his son Elfwine in his old age, and he to his son Theoden II, who rules Rohan now in the Fifth age.
Gondor is experiencing a time of plenty as it never has before. The Lands of Gondor stretch down to encompass Ithilien in the south, and swing behind Mount Mindolluin to connect through the Enedwaith with Arnor, the great kingdom of men to the North. Recently, however, the south-easternmost fortress (formerly Minas Morgul) was taken by the enemy, and is slowly being perverted once again.
Rohan, having long ago sworn undying fealty to Gondor, has expanded only to encompass the lands they once held (but lost) during the Third Age. The Rohirrim are still the greatest horsemen in all the kingdoms of elves, men, and dwarves, and they act as a force on retainer for Gondor when swift reaction to a threat is necessary.