It's basically DEFCON, just with some modern design sensibilities.
If you never played DEFCON, it was a game about essentially planning as best as possible for a thermo-nuclear war which always happens. This involved placement of military assets, such as fleets, air forces etc. but also about the placement of defensive weapons as well. The war kicks off, nukes goes flying and you see how well you did - rinse and repeat.
As far as I've read, this is basically the same thing, except it has a tech tree you can go down and a bit more agency to build things and lean into specific strategies.
But it's a game about firing nukes at other people, nothing more, nothing less.