Not a deterrent 

In the previous version of this article, the R-16 was referred to as "the first truly credible rocket-based nuclear deterrent" in the Soviet arsenal.  This is inaccurate  the long response time and unprotected launch facilities meant that the R-16 was a first-strike weapon only (as was its counterpart the Atlas), because in case of a surprise first strike by the US, all these missiles would have been blown to bits before they could even be fueled for launch.  I've changed the text to "the first truly successful intercontinental ballistic missile". 24.5.122.13