In late 2016, the U.S. defense establishment arrived at a consensus: with just 275 frontline ships, the U.S. Navy was too small to maintain a forward presence across the world’s oceans, deter Russia and China and support combat operations in the Persian Gulf and Central Asia.

Both the Obama administration and the future Trump administration endorsed a new goal of around 350 ships. The U.S. Congress codified a 355-ship Navy in the 2018 defense authorization act. By mid-2018, the idea of a bigger fleet enjoyed widespread support across the U.S. political and military establishments.

But turning the idea of a bigger fleet into an actual bigger fleet has proved difficult, at best. One Congressional shipbuilding expert actually insisted, on condition of anonymity, that quickly growing the Navy by 75 ships simply by buying new vessels “would be impossible.”

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The Navy clearly understands this, and is planning to supplement new ship-construction with life-extensions for existing vessels. But it’s unclear how viable, and expensive, the extensions might be.

From a recent peak of 568 frontline ships in 1987, the Navy shrank to a low of 271 ships in 2015. To be fair, those 271 ships were, on average, larger and more heavily-armed than the typical vessel from 30 years prior.

But a ship can only be in one place at a time. Donald Trump made a 350-ship a plank of his campaign for president. And in the waning days of the Obama administration, outgoing Navy secretary Ray Mabus conducted a force-structure analysis that called for 355 ships. “All of the analysis done to date, inside and outside of the Navy, recognizes, as we have for nearly the last eight years, the need for a larger fleet,” Mabus wrote.

Adding at least 75 vessels during a hypothetical, two-term Trump presidency lasting eight years would require the administration to plan for, and Congress to fund, as many as 15 new ships every year — six to replace older ships in the process of decommissioning plus another nine to actually expand the fleet.

Manufacturing and maintaining the extra ships could cost as much as $23 billion a year, according to a 2017 report from the Congressional Research Service. For years, the Navy’s annual shipbuilding budget has been around $15 billion.

Trump was slow to even try fulfilling his campaign promise and make good on Mabus’s assessment. In his first budget proposal, for 2018, Trump requested just nine new ships, one fewer than Obama bought, on average, during the final years of his presidency.

Richard V. Spencer, Trump’s nominee for Navy secretary, tried to walk back the 355-ship goal during his July 2017 confirmation hearing. “What I will tell you is that whether it’s a 355-ship [fleet] or not, what we also want to get our head around is, can we have a capacity number but have a capability that’s even greater than that, [to] have the capability of a 355- that might be a 300-ship Navy,” Spencer said.

Congress ultimately rejected Trump’s proposal and instead funded 14 new ships for $24 billion in 2018. The Navy then proposed buying 54 new ships between 2019 and 2023, part of a plan to acquire as many as 326 vessels through 2049, for an average of 10 new ships per year. The total bill for the fleet build-up could exceed $600 billion.

But even that plan alone wouldn’t result in a 355-ship fleet. In a July 2018 report, the Congressional Research Service projected that that Navy’s 2019 plan would grow the fleet to a peak of 342 ships in 2039 and 2041. The Navy would then shrink to 335 vessels by the end of the 2040s.

Recognizing the likely limits on new construction, the Navy explored alternative methods of boosting ship numbers. The service briefly considered reactivating decommissioned frigates and even the old aircraft carrier Kitty Hawk, laid up in Washington State since leaving the fleet in 2009.

Instead of reactivating old ships, in April 2018 the Navy settled on a plan to extend the lives of vessels currently in service. Most notably, all Arleigh Burke-class destroyers — there are 77 of the destroyers in service, building or under contract — would remain in the fleet at least 45 years each, up from 35 or 40 years under previous planning.

Keeping destroyers and some other ship types in service longer would help grow the fleet to 355 ships sometime in the 2030s, Vice Adm. Bill Merz, a deputy chief of naval operations, told lawmakers.

But Mertz admitted that Navy hadn’t actually determined, on a ship-by-ship basis, whether all of the Burkes are in adequate condition to serve for 45 years without significant additional maintenance. Instead, the Navy decided that the Burkes should be able to sail longer “based on the performance of the class.”

Likewise, the Navy hadn’t estimated the cost of upgrading the destroyers’ combat systems to keep them relevant in their fourth and fifth decades of service. “We’ll have to learn how to pay for that,” Mertz said.

All of the Navy’s plans for a bigger fleet hinge on one thing: sustained bigger budgets. Even the most modest scheme requires spending more than $20 billion a year on new ships alone for the foreseeable future — $5 billion more than the recent average. It’s worth noting that the Trump administration’s 2018 tax cuts are projected to swell the annual U.S. budget deficit to $1 trillion, a record gap in a health economy.

The $20 billion the Navy expects to spend every year on growing the fleet doesn’t include the cost of arming, manning, operating and maintaining the extra ships. The Congressional Research Service warned that, realistically, a bigger fleet could eventually require the Pentagon to make difficult trade-offs. “Depending on total levels of defense spending in coming years, achieving and maintaining a 355-ship fleet could require reducing funding levels for other Department of Defense programs.”

This first appeared in WarIsBoring here.