You control the sea, air, land, and finally space. You would have complete dominance that would render ICBM's moot.
Perhaps that's a use case for some type of space based directed energy weapon if you could somehow minimize the atmospheric losses to maintain effectiveness.
this is far more useful for anything that is sigint/communications based, or space based radar, than anything as a weapon.
Although not to the same level of accuracy as "hovering" over a specific longitude along the equator as in geostationary.
https://en.wikipedia.org/wiki/Space_Battleship_Yamato_(1977_...
Like many modern computer games:
Mission brief: "You have a mission of the utmost..."
Me: clicks skip "Go in, shoot stuff, got it."
Gravity. This thing is going to be huge, weigh many, many thousands of tons. Having it fly on vertical thrust is probably going to take more fuel than it can realistically carry, and certainly more than you can realistically supply it with. If you're going to do something like this, I think you need to look at lighter-than-air airships. Or maybe something hybrid?