These smaller spin-off titles, according to The Creative Assembly, will contain the same turn-based campaign and real-time combat that we've come to expect from Total War games, however they'll focus exclusively on conflicts that last only a few weeks or months. The games will only encompass a few months or a few decades at most, while still carrying through with the same mix of turn-based campaign strategy and real-time tactics.
Games director for the Sagas Jack Lusted explained a little more about the new plans on the Total War Website, including a definition of what makes the game a Total War Saga.
These will be a new class of historical Total War game, focused on "powder keg" moments in history, when the course of the world was decided in a short sliver of time and space - such as, in CA's words: "civil wars, renowned conquests, and political upheavals".
We're told to expect the first Saga before the next major historical title, which Creative Assembly said is well into development. There might be as many playable factions or conquerable territories in them, but that could all be focused down to one specific region or country and a particular point in time. He stressed that it is not a major historical release and is only an iteration on a previous game. It will be fully revealed over the next few months.
To be more precise, the first Total War Saga game will have a map as big as Attila gameplay-wise, and a campaign will last just as long, but the scale will be different, with the map covering a much smaller area in actual miles. In "Saga", the focus will take on moments instead. This makes them a flawless fit for Total War games, where we give players the freedom to depart from the actual historical events and explore what might have happened had things gone differently.
The only mentioned title, so far, will be a follow-up to Total War: Rome II in the vein of Total War: Atilla. "Especially for a moment in history we've not spent enough time with yet as a studio".