While I agree this will be a major boon for SpaceX because military gonna military, in realistic terms it's far from a game changer. ICBMs are tough to shoot down because of their high speed and small size. Starship, by contrast, is huge and will need to slow down much more when reentering the atmosphere. It would be a sitting duck.
For proxy and "we're not involved in this war, honest" type stuff, that might be acceptable so long as target is nowhere near peer. But in any war against a peer military power including Russia/China, they'd have about as much use as aircraft carriers - which is to say, basically none. This, btw, is the major problem with war logistics in general. It's not the speed, because throughput matters much more than latency anyhow, but vulnerability.
For proxy and "we're not involved in this war, honest" type stuff, that might be acceptable so long as target is nowhere near peer. But in any war against a peer military power including Russia/China, they'd have about as much use as aircraft carriers - which is to say, basically none. This, btw, is the major problem with war logistics in general. It's not the speed, because throughput matters much more than latency anyhow, but vulnerability.