"As a nation, we have to have the discussion about how much we value that capability, why it is important, why it keeps us a great power and why each leg of the triad makes each of the other legs that much more credible," he added. "Those are important questions we need to be able to ask and answer."
In January 2015, the Congressional Budget Office estimated the nuclear arsenal will cost $348 billion to upgrade and maintain over the next decade, while an August 2015 study by the Center for Strategic and Budgetary Assessments found that upgrading and maintaining the US nuclear force posture will cost more than $700 billion over the next 25 years.
"In our history, every time that has happened, we have added a specific amount to the Defense Department's top line to accommodate the modernization of our strategic nuclear arsenal," Selva said of the coming costs. "That is a substantial bill for the nation to pay.
"If we are not starting that discussion right now, this instant, it will be too late," he concluded. "We are already formulating the [Program Objective Memorandum] that defines the top line for the early '20s. We have to get this conversation to the forefront."
Selva seemed to argue that the triad — the naval, air and ICBM nuclear delivery arms of the Pentagon — needs to take precedent over conventional systems, given its centrality to American global power projection.
"Our capacity to deter nuclear foes adds credibility to our conventional force, and if we are ever threatened by a nuclear foe who is our equal or our better, then our conventional force loses relevance quick," Selva said.
As the general painted it, the issue of explaining the need for a nuclear triad ties into a broader cultural divide between those under 40 and those over 40 on national security issues as a whole.
Those under 40, he argued, generally do not see national security as a major discussion topic the way it is for an older generation.
"The debate about national security disappeared, in any real measure, from our national dialogue" post Desert Storm, he said. "9/11 made it worse, not better, because 9/11 made national security about counter terrorism … broad strategic conversation about the value of the military outside of that context was lost."
Fixing that, and finding a way to inject substantive conversation about defense issues back into the everyday discourse, is a heavy load, Selva said.
"College professors have to say it's important. High school teachers have to say it's important. Clergy have to understand," he said. "And how do you motivate them to have that conversation? I don't know."
Aaron Mehta was deputy editor and senior Pentagon correspondent for Defense News, covering policy, strategy and acquisition at the highest levels of the Defense Department and its international partners.