4) Middle-earth’s international relations were complex.
The IR paradigm of polarity applies quite readily to Middle-earth. The First Age was one in which the first Dark Lord, Morgoth, created a literal Hell on Arda (“earth”) and used that as a base from which to impose his direct unipolar rule, not just hegemony, over all Middle-earth. Despite the heroic efforts of the Elves and their allies of Men, he would have succeeded had not the Valar, the one god Eru’s angelic deputies, intervened with massive, cosmic power. The Second Age was one of bipolar, dueling hegemonies: in the west and coastlands of Middle-earth, Númenor held sway; in the east, Sauron was the dominant power. Twice in that era the Númenóreans swept Sauron’s forces aside like chaff, and while the first time they pulled back to their island kingdom, the second time—in the last century of the Second Age—they briefly ruled all of Middle-earth, except for some of the small Elven realms. The Third Age began with Sauron’s almost-total unipolar control, which was defeated by the Last Alliance of Men and Elves and replaced by the more benevolent hegemony of Arnor and Gondor. But after the northern kingdom was destroyed, and after Gondor’s brief hegemonic moment in the 12th century of this Age, Middle-earth devolved into a multi-polar arrangement with several power blocs: even a reduced Gondor was primus inter pares but other powerful states existed, such as Mordor, Rohan, Rhovanion, Harad, Erebor, and the Elven realms such as Thranduil’s Woodland one.
The Reunited Kingdom of Elessar (Aragorn II), which to a rejuvenated Gondor added the old Arnor—think the Byzantine Empire successfully re-integrating the old Roman Western Empire—was approximately the same size as Gondor at the height of its power 1800 years earlier, but hegemonic, not imperial. This situation continued into the Fourth Age, as far as Tolkien’s history records.
5) Strategy, tactics, leadership and good militaries won wars—not magic.
Despite its reputation as a fantasy world, Middle-earth is very much one where, as Tolkien put it, “miles are miles, days are days, and weather is weather.” OK, there are exceptions to this: at one crucial point in the Third Age, the powerful Elf Galadriel sent a time-slowing fog to encompass the ancestors of the Rohirrim riding to help Gondor defeat a massive Easterling and Orc invasion. And later, of course, Sauron is finally discorporealized by melting his One Ruling Ring. But in both cases, it was warfare that actually brought about victory (even if indirectly, in the War of the Ring). In almost all of the 24 most important conflicts across space and time in Middle-earth, a commander would have been better off having attended Minas Tirith Military Academy than, say, Saurman’s School for Wayward Wizards. Aragorn moved from a non-state asymmetric warrior (Ranger of the North) to commander of a state military (leading the combined Gondorian heavy infantry and Rohirrim heavy cavalry) and, then, to actual King. That reforged broken sword didn’t hurt, but it had no magical powers beyond the ability to inspire. The most important battle of the Third Age (if not the biggest), that of the Pelennor Fields, was won when Théoden King of Rohan broke the lines of Mordor by leading a cavalry charge—not by Gandalf besting the Witch-King in wizardry. And so on.