[evo]

I actually wouldn't be surprised if it did have a direct VLF antenna system. If the Dead Hand had triggered, that suggests multiple Soviet C&C headquarters went offline due to a first strike, and at that point you can't really assume your repeaters or silos are still online. The submarine fleet's primary purpose is to be the surviving second strike capacity.

[TheOtherHobbes]

Both the US and Russia have flying command systems which use very long trailing wires to send launch commands.

The problem: they're nearly a single point of failure. If you can hit the other side's command systems their missiles won't be going anywhere.

I'd assume both sides know this and contingencies and redundancies exist.