Editing Submarine-launched ballistic missile (section)

===Deployment and further development===
The short range of the early SLBMs dictated basing and deployment locations. By the late 1960s the Polaris A-3 was deployed on all US SSBNs with a range of {{convert|4600|km|nmi}}, a great improvement on the {{convert|1900|km|nmi}} range of Polaris A-1.  The A-3 also had three warheads that landed in a pattern around a single target.<ref>Friedman, pp. 199–200</ref><ref>Polmar American Submarine, pp. 131–133</ref> The Yankee class was initially equipped with the [[R-27 Zyb]] missile (SS-N-6) with a range of {{convert|2400|km|nmi}}. The US was much more fortunate in its basing arrangements than the Soviets. Thanks to [[NATO]] and the US possession of [[Guam]], US SSBNs were permanently forward deployed at Advanced Refit Sites in [[Holy Loch]], Scotland, [[Naval Station Rota|Rota, Spain]], and Guam by the middle 1960s, resulting in short transit times to patrol areas near the Soviet Union. The SSBN facilities at the Advanced Refit Sites were austere, with only a [[submarine tender]] and [[floating dry dock]]. Converted merchant ships [[hull classification symbol|designated T-AKs]] ([[Military Sealift Command]] cargo ships) were provided to ferry missiles and supplies to the sites. With two rotating crews per boat, about one-third of the total US force could be in a patrol area at any time. The Soviet bases, in [[Severomorsk]] (near [[Murmansk]])  for the [[Arctic Ocean|Arctic]]-[[Atlantic Ocean|Atlantic]] theater in [[Petropavlovsk-Kamchatsky]] for the [[Pacific Ocean|Pacific]] theater, required their SSBNs to make a long transit (e.g., through NATO-monitored waters in the Atlantic) to their mid-ocean patrol areas to hold the continental United States ([[CONUS]]) at risk. This resulted in only a small percentage of the Soviet force occupying patrol areas at any time, and was a great motivation for longer-range Soviet SLBMs, which would allow them to patrol close to their bases, in areas sometimes referred to as "deep bastions". These missiles were the [[R-29 Vysota]] series (SS-N-8, SS-N-18, SS-N-23), equipped on [[Delta-class submarine|Projects 667B, 667BD, 667BDR, and 667BDRM]] (Delta-I through Delta-IV classes).<ref name="Gardiner and Chumbley, pp. 355–357"/> The SS-N-8, with a range of {{convert|7700|km|nmi}}, entered service on the first Delta-I boat in 1972, before the Yankee class was even completed. A total of 43 Delta-class boats of all types entered service 1972–90, with the SS-N-18 on the Delta III class and the [[R-29RM Shtil]] (SS-N-23) on the Delta IV class.<ref>{{cite web|url=http://russianships.info/eng/submarines/project_667b.htm|title=Nuclear-powered ballistic missile submarines – Project 667B|website=russianships.info}}</ref><ref>{{cite web|url=http://russianships.info/eng/submarines/project_667bd.htm|title=Nuclear-powered ballistic missile submarines – Project 667BD|website=russianships.info}}</ref><ref>{{cite web|url=http://russianships.info/eng/submarines/project_667bdr.htm|title=Nuclear-powered ballistic missile submarines – Project 667BDR|website=russianships.info}}</ref><ref>{{cite web|url=http://russianships.info/eng/submarines/project_667bdrm.htm|title=Nuclear-powered ballistic missile submarines – Project 667BDRM|website=russianships.info}}</ref> The new missiles had increased range and eventually multiple independently targetable reentry vehicles ([[MIRV]]), multiple warheads that could each hit a different target.<ref name="Gardiner and Chumbley, pp. 355–357"/>