[Rumil]

It does seem that the military technology of Midddle Earth actually declined somewhat.

Elrond refers to a 'host of elves in armour of old' or somesuch, implying that the Third Age armour was inferior to what was used in the First Age perhaps? Certainly the Gate-Guards of Gondolin had some visually impressive stuff but the exact type of armour is not described in detail.

I wonder if the 1st Age Elves had discovered face-hardening, a metallurgical technique that makes armour practically arrow-proof? Or could be that they had plenty of Mithril!

Also the steel bows of the 2nd Age Numenoreans are mentioned, but no hint of them in the Third Age.

At least we can be sure that the stirrup was used by cavalry, as Eowyn mentions the stirrup-cup.