In my latest Diplomat column I make the case for retaining a (reduced) boomer fleet:
My own view is that the United States can accept a lower threshold for at sea nuclear deterrence, but this leg should still retain a rump deterrence capability. Survivability concerns may not be what they were, but they are still relevant, and SSBNs have both survivability and flexibility advantages over ICBMs. It isn’t accidental that China, India, and Russia are all choosing to develop or upgrade their SSBN capabilities at the same time. Concerns about shipbuilding costs should be remedied by resource transfers between services; if the Air Force no longer operates an ICBM force, then funding can (at least theoretically) shift towards the Navy.
Replacement of the Ohio boats will still be expensive, but circumstances may allow life extension beyond current expectations. The long term answer may not be an entirely new SSBN design, but rather a modified Virginia class boat that could carry ballistic missiles. The Navy has argued that this design would become more expensive than an Ohio replacement, but issues of number and vulnerability may prove more manageable if the option is no boomers at all. No other state in the world can match such a capability, and yet the U.S. presumably feels deterred from launching pre-emptive nuclear attacks on China or Russia. A reduced SSBN force is still the best option for providing a foundational level of nuclear security.
Here’s some more on the aging ICBM force.