The Navy’s operations, on which the sun never sets, are the nation’s nerve endings, connecting it with the turbulent world. Although the next president may be elected without addressing the Navy’s proper size and configuration, for four years he or she will be acutely aware of where the carriers are. Today they are at the center of a debate about their continuing centrality, even viability, in the Navy’s projection of force.

Far out into the South China Sea, China is manufacturing mini-islands out of reefs, many of which used to be underwater at high tide. China is asserting sovereignty above and around these militarized specks in the congested cauldron of this sea. Through it and adjoining straits pass half the world’s seaborne tonnage; five of America’s most important 15 trading partners are in this region. Until President Trump launches his many trade wars, those partners include China, which is America’s third-largest export market and largest source of imports. The Obama administration has rejected challenging China’s audacity by not sailing through its claimed territorial waters — within 12 miles — around the new reef-islands.

Henry J. Hendrix of the Center for a New American Security argues that, like the battleships which carriers were originally designed to support, carriers may now be too expensive and vulnerable. China has developed land-based anti-ship missiles to force carriers to operate so far from targets that manned aircraft might become less useful than unmanned combat aerial vehicles (UCAVs) operating from smaller, less expensive carriers.

The newest carrier, the USS Gerald R. Ford, to be commissioned next year, costs $12.8 billion. Add the costs of the air wing, the support of five surface combat ships and one attack submarine, and 6,700 sailors. The bill for operating a carrier group: $2.5 million a day. China, says Hendrix, could build more than 1,200 of its premier anti-ship missiles for the cost of one Ford carrier, and one of the 1,200 could achieve “mission-kill,” removing the carrier from the fight for months.

The bad news is that America’s entitlement state is devouring the federal budget. The good news might be this axiom: As money gets scarcer, people get smarter.

It might be smart to reduce spending on the astonishingly expensive and operationally dubious F-35 Joint Strike Fighter, and redirect the money to unmanned combat aircraft that could extend, for a while, the carriers’ viability. For $3 billion the Navy could have 10 more nimble littoral combat ships providing increased day-to-day presence. Furthermore, of the 14 Ohio-class ballistic missile submarines that were built for 30-year lives, the youngest is 17 and all might be kept in service until they are 40. Buying conventional guided-missile variants of these stealthy arsenals would bring many precision-strike missiles close to land targets, obviating anti-surface-ship missiles. The undersea component of the Navy is the most survivable, but it is not inexpensive: The first replacement of the Ohio-class submarines, due in 2021, will cost $9 billion, with subsequent ones costing about $5 billion in 2010 dollars.

War-fighting calculations are not, however, the only pertinent considerations. The Navy remains the primary manifestation of America’s military presence in the world, and carriers are, beyond their versatility, an especially emphatic presence. The Navy believes it does not need more than 11 carriers (counting the Ford), but that it cannot perform its myriad missions, from preserving the free flow of world commerce to bringing air power within range of the Islamic State, with fewer.

Day by day, hour by hour, there is no more complicated government job than that of the chief of naval operations (CNO). Beyond the management of moving pieces in every time zone, the CNO must attend to the maintenance of an industrial base capable of sustaining technological advantages with weapons systems that take decades moving from conception to deployment.

Adm. Jonathan Greenert, who stepped down as CNO last month, says Chinese carriers are “rudimentary” but their pace of improvement is “extraordinary.” Also extraordinary, given America’s current political climate, is the bipartisan agreement that the Navy must grow. The Obama administration’s budget calls for the active duty fleet, which today has 273 ships, to reach more than 300 by 2020.

America was blown into world affairs by the 1898 explosion — an accident mistakenly blamed on Spain — that sank the USS Maine in Havana harbor. The Navy America chooses to maintain always indicates the nation’s current sense of its character and destiny. So, presidential aspirants — parsimonious Republicans and militarily ambivalent Democrats — should talk about the Navy they want to wield.

© 2015, Washington Post Writers Group