 The return of "Proteus" to Guam marked the end of the first significant time period that "Proteus" had been absent from Guam since establishing SSBN REFIT Site III in 1964.The replacement of 616-class SSBNs with 598/608-class SSBNs commenced in May 1973 when departed for conversion to the Poseidon Weapons System, and was relieved by .Later in 1973 and replaced and .