https://nap.nationalacademies.org/catalog/13189/making-sense...
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This compares to ~20-30min for existing ICBMs and their ground based interceptors
In particular, when the goal is to intercept an ICBM, the enemy helpfully raises the target to be (briefly) at the same altitude as the satellite. (An ICBM's max altitude is much higher than low-earth orbit.) If the goal is for a satellite to attack a city, the enemy does not helpfully raise the city to orbital altitudes.
I also understand that those nukes regularly get deliciously close to their targets (100 miles or so) (delicious from the point of view of the attacker).
I stand by my assertion however: to be explicit, for the same energy budget, it is quicker to hit a target from the ground half-way around the world from the target than it is to hit the target from orbit even if the satellite is directly above the target. The exception to that is laser weapons because a laser beam has no momentum whereas all the "strategic" nukes in the US arsenal weigh at least 200 lb, which is a lot of momentum when moving at orbital speed.
(Also, it is vastly cheaper to maintain infrastructure on the ground than in orbit.)
See Fractional Orbital Bombardment. China tested theirs last year.
...SpaceX people are building it here: https://www.castelion.com/team
I also don't understand why intercepting faster is worth anything.
If you look at Starlink orbits, every single satellite in the constellation goes over any given point on Earth (e.g. Moscow) within a 12 hour period.
So if the conflict lasts that long, the whole constellation can be unloaded.