An Examination of Elrond's Army in the War for Middle-earth

The question of how the war for Middle-earth would have been affected if Elrond brought his entire army to attack the forces of Mordor and aid Gondor is a fascinating one, especially when considering the vastly different historical contexts of The Lord of the Rings (Tolkein's books and movies).

Rivendell: A Haven for the Elves

In the detailed world of Middle-earth, Rivendell was not a nation nor a place of large-scale military endeavors. Tolkien, in his The Lord of the Rings books, often kept the focus on the political and military actions of Mordor, Gondor, and Rivendell's involvement, which was mostly in support of the war effort. Rivendell was a small and hidden community of elves. Tolkien did not provide exact numbers, but it is reasonable to conclude that the population was not significant enough to form a large army.

The Size of Rivendell's Forces

Tolkein’s depiction of Rivendell often portrayed a scene of tranquility with a few elves, mostly housed in a single building, surrounded by trees. There is no room, literally, for an army. When Halbarad, the Ranger, and 30 of the Dúnedain of the North arrived in Rohan with Elrond’s sons Elladan and Elrohir, one might reasonably interpret this as Elrond sending his entire army to aid Aragorn, especially considering the few elves remaining in Rivendell.

The War of the Ring

In the world of the War of the Ring, Elrond's influence was mainly through his sons and healers like Glorfindel. Sauron's threats extended to Lothlórien, Mirkwood, Dale, and Erebor, but these events are not always elaborated upon in the books. It is possible that other threats in the North required the full attention of Rivendell, leading to speculative narratives in video games and adaptations.

The Second Age

During the Second Age, Rivendell was a refuge for the Noldorin forces. Elrond, as the Herald of Gil-galad, was part of the High King's army and played a crucial role in the War of the Last Alliance. By the time of the events in The Lord of the Rings, most of the Noldorin had returned to their homes across the sea, leaving Rivendell as a small family community, not a place capable of fielding a substantial army.

Conclusion

In summary, while Elrond could have brought strength to the war effort during the Second Age, by the time of the War of the Ring, his forces were sparse and could not have made a significant impact against Mordor's vast army. Rivendell's role was more one of support through information, intelligence, and occasional military support rather than leading a massive offensive.

Through various historical contexts, we can see that while Elrond's involvement might have been significant, it would not have been in a traditional military sense, rather through strategic, supportive, and advisory roles.