Sentence:  For example , the importance of the Regulus 2 , , a very promising aerodynamic ship to surface missile designed to be launched by surfaced <WSD>submarines</WSD> , was greatly diminished by the successful acceleration of the much more advanced Polaris ballistic missile launched by submerged submarines . 
Meaning of the word marked with <WSD> tags:  a submersible warship usually armed with torpedoes