This also sounds a bit like Planetside 2 [1], which had a similar structure. A relatively large open world where small "provinces" were contested by factions in FPS King-of-the-Hill combat. This meant that any one province action was a part of a larger "front," across which factions would often mass & press offensives. Capturing the entire map led to some kind of reward, and then a reset iirc.

Nothing like rolling up in an APC with 12 people in voice chat on the tip of the spear, or coordinating an entire battery of MAXs keeping the skies clear. Some of the best gaming in general I've ever experienced. Gradually, though, pay to win mechanics pushed me away, and I've not played since 2014.

[1]: https://en.wikipedia.org/wiki/PlanetSide_2