There have been plenty of "warlords" in fantasy fiction.
1) Merlin (King Arthur)
2) Brynden Tully aka "the Blackfish" (A Song of Ice and Fire)
3) General Kael (Willow)
4) Aragorn and Faramir (Lord of the Rings)
5) Matrim, Gareth Bryne (Wheel of Time)
Five (plus) characters from five separate series.
This doesn't even take into account large numbers of characters in DnD novels, like Daine (Eberron novels, the Dreaming Dark series), Azriim (a slaad who featured in a chapter called "Senseless Slaughter, Sensibly Done" in the Erevis Cale series), or many characters in the Drizzt series (Obould I, Drizzt, Jarlaxle, etc).
I find it mystifying that people don't remember such characters.