An SSBN is not designed to fight through the fleet line like a battleship or surface combatant. Its mission is nation-against-nation deterrence through ballistic missiles. It still qualifies as a capital ship because its existence changes strategic decisions at the highest level. Capital status is defined here by political effect rather than size, armour, or tactical position.
Notable Point · 4:22:42-4:23:07
Why ballistic-missile submarines are capital ships
Ballistic-missile submarines sit outside the battle line but qualify as capital ships because they exert strategic influence at the level of states.