After a decade of delayed and reduced budgets, one of the few elements of President Trump’s campaign and ensuing administration that has garnered little criticism from the other side of the political fence has been his efforts to bring the American defense apparatus back to a passable state of readiness.

Multiple bipartisan reports have confirmed that America’s military supremacy is no longer assured, following two decades of ongoing combat operations in the Middle East and corresponding stagnation when it comes to developing new weapons technology aimed at a conflict with a peer-level adversary. Under Trump, the Defense Department received a much-needed influx of cash this fiscal year, but as experts quickly assessed, even the largest defense budget in the nation’s history isn’t enough to repair a decade’s worth of neglect and fund a massive buildup of military hardware like Trump promised on his way to Pennsylvania Avenue.

One of the president’s biggest talking points was the idea of a 355-ship Navy — a massive increase from its current 280 or so vessels. The Navy does expect the number of ships under its flag to grow by some 46 vessels over the next five or so years, but many others will be reaching the ends of their service lives during that same span of time.

“If the Navy adheres to the schedule for retiring ships outlined in the 2019 plan, it would not meet its goal of 355 ships at any time over the next 30 years,” a report from the Congressional Budget Office released last month read.

To date, the Navy doesn’t actually know when it could reach Trump’s proposed 355 ships, but doing so within decades would require a great deal more funding — either to build more ships or to modernize dated platforms sufficiently to keep them in the force. The result would be a massive Navy, particularly in regard to surface ships, which are cheaper to produce or to extend their service lives.

Unfortunately, even if the funding to reach that much-touted number could be allocated, the effort may be hindered by a different pressing need that holds a higher priority to the nation’s defense posture: America’s aging ballistic missile submarines need replacements. According to statements made by a panel of security and budgetary experts earlier this week, the U.S. Navy will likely be able to fund one endeavor, but not both.

“There is not enough money for both,” the panel concluded, adding, “priorities need to be taken.”

While Russia has placed a renewed emphasis on its own submarine force, America’s need to build more Columbia-class ballistic missile submarines to replace its aging fleet of Ohio-class subs isn’t about countering the presence of enemy ships, but rather about maintaining the nation’s “second strike” capability. America’s nuclear triad (three avenues of launching nuclear attacks: via aircraft, ICBM, and submarine) is meant to serve primarily as a powerful nuclear deterrent.

By dividing nuclear weapons across multiple domains, the United States ensures no attack could neuter America’s nuclear response. Without the nuclear triad, mutually assured destruction goes back to being a phrase instead of an effective defensive strategy. Put simply, there has been no indication that Washington will give the Pentagon enough money to both keep the submersible leg of the nuclear triad operational and expand the size of the Navy’s surface fleet, especially now that Democrats have secured Congress.

“The Navy shouldn’t be allowed to say, ‘sorry, we ran out of money’ when it comes to paying for the ballistic missile submarine because the shipbuilding account was used for other kinds of warships,” Jim Miller, a former undersecretary of Defense for policy, said. “The Navy needs to step up to that bill.”