Xeviat
Dungeon Mistress, she/her
Open question here; I've heard some good examples of character people would call warlords (Captain America, Robin Hood, Odysseus), but I'd argue those people could just as easily be called Battlemasters.
They were all definitely skilled warriors in their own rights. Captain America, for one, is one of the most skilled warriors in the Marvel universe, and is only really bested because the rest of his powers are basically just having 18-20 in all his stats (peak human) alongside characters with more ridiculous powers. On his own, without allies to direct, Captain America is still going to kick butt, and that feels like a fighter (He also fits my model of "fighters fight with technique", while other classes fight with instinct or trickery or supernatural power).
I do not understand the insistence of some for historical example. D&D in many areas over it's history has been self referential. Most example lead to calls that figure would be a fighter. As I said earlier that the fighter swallows almost everything that does not use magic but mechanically speaking on pays lip service.
This is actually really important to me. All of the D&D classes are based off of something, BUT some of them are based off a really small thing. The Bard, Paladin, and Ranger aren't concepts that are everywhere, but D&D made them nearly ubiquitous. They are definitely self referential. So, it is an important question to ask, but not the most important. At best, asking it helps to gather ideas for what the class can do.
3.5 had the Soul Knife as a whole class, and that wasn't based on a whole lot. Thus, many of us want to see it as a subclass.
And that's really the discussion here: class vs. subclass. I think putting the Warlord into other classes would make those other classes broader and better.