[dragonwriter]

> The very concept of the letters presupposes that sub crews have full control over their missiles, that they can fire them based on instructions in a hand-written letter. That does not mesh with the safeguards surrounding other weapons that require external command/codes prior to launch.

The whole point of the submarine component of the strategic triad is to be the ultimate guarantor of MAD by presenting the capacity for launching a retaliatory strike in the event of sudden destruction of the highest command authorities (and, potentially, the land-based components of the triad), so it is absolutely plausible that submarines have a looser set of controls than bombers and land-based missiles because otherwise there would be no point in having them.

[arethuza]

And in the case of the UK we don't have a triad - just the 4 Vanguard-class boats.