When presidential candidate Donald Trump in late 2016 announced his plan to grow the U.S. Navy from today's 275 front-line warships to a whopping 350 ships, Trump's supporters applauded. Unsurprisingly, Navy officials were also pleased.

But professional naval analysts rolled their eyes. They knew what Trump apparently didn't know — or at least refused to admit in public. Building ships is expensive and time-consuming. A 350-ship Navy isn't impossible. It's just really, really hard.

Now half a year later, the Trump administration has proposed its first full budget, for the 2018 fiscal year. The budget proposal includes $603 billion for the Defense Department — an $18-billion increase over what President Barack Obama's administration had projected for 2018.

But there's no trace of candidate Trump's plan to expand the fleet. Instead, Trump is asking for just eight new ships, locking the Navy — at least for the next couple of years with this build rate — into a much more modest expansion to no more than 308 vessels. An expansion begun by Obama nearly a decade ago.

That's right. Unless something dramatic happens soon, Trump's navy will end looking a lot like Obama's navy. And while Democrats, small-government libertarians, and peace-advocates might be pleased with such an outcome, hawkish Republicans and Navy leaders are already noisily protesting.

"This budget request fails to provide the necessary resources to restore military readiness, rebuild military capacity and renew our military advantage with investments in modern capabilities," stated Arizona senator John McCain, a Republican.

"The Navy must get to work now to both build more ships, and to think forward—innovate—as we go," Adm. John Richardson, the Navy's top officer, wrote in a May 2017 study—emphasis his. "To remain competitive, we must start today and we must improve faster."

A bigger Navy would mark a major reversal of long-term trends. At the end of the Cold War, the then-600-strong U.S. combat fleet — including aircraft carriers, amphibious ships, destroyers and other "surface combatants" plus submarines — rapidly declined as successive administrations cut the Pentagon's budget.

The decline continued even when defense budgets climbed back to Cold War levels in the aftermath of 9/11. Pres. George W. Bush's military priorities were in Iraq and Afghanistan, not on the high seas. By the end of Bush's second term, the fleet had bottomed out at around 280 frontline vessels.

Under Bush the Navy built an average of between six and seven new warships annually. As most ships serve for 30 or 40 years before wearing out or becoming obsolete, Bush's $12-billion yearly shipbuilding budgets sustained a long-term fleet of no more than 230 ships.

Obama and his long-serving Navy secretary Ray Mabus significantly boosted shipbuilding accounts to an average of $15 billion annually. During the Obama years the Navy acquired an average of nearly nine new ships per year for a long-term fleet of some 310 vessels — two more than Obama's official goal of building a 308-ship Navy by the mid-2020s.

308 ships might have seemed adequate nearly a decade ago. But with both Russia and China growing and modernizing their own fleets, by 2016 the Navy had decided it needed more ships. Lots more. One of Mabus' final acts before stepping down in January 2017 was to officially endorse a so-called "Force Structure Assessment," or FSA, calling for a 355-ship Navy -- five more ships than Trump was calling for at the same time.

But the Navy acknowledged that adding nearly 50 vessels to Obama's 308-ship plan would be expensive -- and could even exceed the spending caps Congress imposed on itself as part of the 2011 Budget Control Act. "The 2016 FSA was not constrained by Budget Control Act funding levels," the Navy stated.

Under Obama the Navy spent $15 billion annually on new ships. Trump's 2018 budget proposal actually cuts shipbuilding funds by a billion dollars compared to 2017. To grow the fleet to at least 350 ships within 30 years could cost the Navy $27 billion annually, according to an April 2017 report from the Congressional Budget Office.

That extra funding would likely put the Pentagon over its spending cap—unless the military finds savings elsewhere. "Achieving and maintaining a 355-ship fleet could require reducing funding levels for other [Defense Department] programs," Ronald O'Rourke, an analyst with the Congressional Research Service, noted in a May 2017 report.

And the spending caps aren't the only obstacle. After two decades of building between six and nine warships per year, the United States' industrial base has sized itself for building ... well, between six and nine warships per year. Getting to 350 or 355 ships requires an annual production rate of between 12 and 15 vessels.

America's seven naval shipyards probably possess enough physical infrastructure—factories, cranes, slipways, drydocks, etc.—to build up to 15 ships a year, according to Eric Wertheim, an independent naval analyst and the author of Combat Fleets of the World. "I do think that the U.S. industrial base can handle additional warship and submarine construction, especially if it's allowed to ramp up over time," Wertheim told The Daily Beast.

However, people could be the biggest problem. "The 355-ship fleet could create thousands of additional manufacturing (and other) jobs at shipyards, associated supplier firms and elsewhere in the U.S. economy," O'Rourke wrote.

But it could take years, or even decades, to train up thousands of new shipyard workers. The two U.S. shipyards that build submarines —Electric Boat in Connecticut and Newport News Shipyard in Virginia— learned this the hard way more than 20 years ago.

"Only two submarines were procured from 1991 to 1998," Lt. Seth Clarke, a Navy spokesperson, told The Daily Beast. "The expertise for submarine construction was dismantled." Around 2005, the Navy decided to begin buying two submarines annually. It took seven years of hiring and training for the shipyards to get ready. It wasn't until 2012 that the Navy could actually begin ordering the extra subs.

Trump wants to grow the attack sub fleet from 52 to 66. The Navy would have to start ordering more than two submarines per year. And that means Newport News and Electric Boat might have to go on another hiring spree.

But it can take up to seven years to train a welder qualified to work on nuclear-powered subs, Will Lennon, an Electric Boat vice president, told Reuters. "In reality, it will likely take even longer than 16 years to get to 66 [submarines] even if all the money in the world is forthcoming," one naval expert who works closely with Congress told The Daily Beast on condition of anonymity, as they were not authorized to speak to the press.

The shipbuilding industry simply isn't ready today to build Trump's bigger fleet — and might not be ready for many years. That lack of readiness, combined with the eye-watering high cost of quickly building scores of extra ships, is the reason why experts never took Trump's plan for a bigger Navy very seriously.

Trump would have to add tens of billions of dollars to Navy accounts every year of his first administration -- and plan for hundreds of billions of dollars in extra funding in the decades following his first term. He'd have to convince Congress that the country can afford all that extra spending and he'd have to rally lawmakers to repeal or amend the Budget Control Act.

Absent all that, the fleet scheme is "more than unrealistic, it would be impossible," the Congressional source said. So it should come as no surprise that, in his first budget proposal, Trump seems to have forgotten about his campaign promise for a huge new U.S. Navy.