What's this?!

[Kuruharan]

Otherwise, the 20th century is rife with examples of democracies demolishing empires.

Those democracies had centralized control over their militaries.

When I say "feudal" mean a situation where military service is promised by one entity (the vassal) to another entity (the lord) in exchange for something, conventionally in the Western useage this meant land. This added a layer of middle management to the military structure that (in many cases) was not responsive to the commands, requests, or timid pleas of the supposed lord. This problem tends to get particularly acute at the highest levels of this middle layer because those individuals are virtually sovereigns themselves (and in some cases are) and have the resources to successfully challenge their titular superior. Such individuals (historically) seemed more interested in bashing each other or trying to overthrow or break away from their supposed sovereign. This is not a recipe for successful empire building of the type Gondor engaged in.

I guess the factor I'm most interested in determining is where the ultimate loyalty of the soldiers lay. If all of them took their oaths to the King/Steward then (theoretically at least) their ultimate loyalty lay with the ruler. If not, then their ultimate loyalty probably lay with their local lord.

I hope I was able to clarify Lalwende's question as well.