Ohio-Class Guided Missile Submarine guided missile submarines SSGN boats Guided Missile Submarines - SSGN guided missile submarines guided missile submarines (SSGNs) 4 guided missile submarines Guided Missile Submarines Guided Missile Submarines replaced them Guided Missile Submarines SSGN Guided Missile Submarines - SSGN guided-missile 4 Guided Missile Submarines weapons Ohio-class models SSGN 4 guided missile submarines 4 Guided Missile Submarines The US Navy -- Fact File