GamesRadar offers "The incredible story of Roman Wars: The lost Call of Duty game," hyping a tale of a proposal that never got past the prototype stage. This doesn't actually stretch credibility all that much, as proposals end at that juncture all the time, but they do offer details on a pitch for an installment in the CoD series set in ancient times. They have a video showing off gameplay of a prototype from Vicarious Visions which includes the CoD logo, though they note this was from a later stage when this was being pitched as a standalone game. Here's how they describe the plan:

The full plan for the game would involve a variety of perspectives and characters, says Polemus. “You were going to play a lead centurion, you were going to play a grunt and you were going to play all the way up to Julius Caesar himself; so you were going to be a commander”. The plot loosely followed ‘Commentarii de Bello Gallico’, otherwise known as Commentaries around the Gallic wars, Julius Caesar’s own account of the battles (Roman War’s main character Titus Pullo is actually named in these accounts as a historical figure).

“You were going to fight against the Germans and the Germanic Tribes and really stay true to the history of Julius’ conquests during the Gallic Wars,” they explain. “You were going to jump around from officers to low grunts to Caesar and get a little variety of all of those little battles, so you’d play an archer here, you’d play a cavalry over in this phase. And it was going to stay true to the Call of Duty franchise in that jumping around, playing those different characters and getting a whole feel of the overall battle during those times”.