GOP presidential hopeful Carly Fiorina put forward an ambitious plan for expanding the U.S. military during the Republican debate Wednesday night. One thing she didn’t mention: How much her plan would cost.

The answer: more than $500 billion—on top of the more than the $5 trillion the Pentagon plans to spend over the next 10 years.

“We need the strongest military on the face of the planet, and everyone has to know it,” Fiorina said Wednesday night, offering specifics about what that would mean under her presidency.

She said she wants 50 Army brigades, 36 Marine battalions, between 300 and 350 naval ships, and an upgrade of “every leg of the nuclear triad.” These numbers seem to be pulled straight from a report released by the conservative Heritage Foundation this year. The conservative think tank says a U.S. military of this size is necessary so that it has the ability to fight and win two major wars at the same time.

Who these wars would be against is unclear. Fiorina did not specify in Wednesday night’s debate either why she thinks the military needs to super-size. To take on China? Invade Iraq again to fight the Islamic State? She mentioned deploying more troops to Europe to deter Russian President Vladimir Putin, but made no mention of a land war with him.

Where she’d get the money to do all of this is also unclear.

It’s safe to assume Fiorina meant 50 active-duty Army brigades, because the Obama administration’s current plan calls for a total of 57 brigades by 2017, if you count the 30 active-duty brigades and the 27 in the National Guard. At its wartime high a few years ago, the Army had 45 brigade combat teams in its active-duty force.

Fiorina’s plan would therefore add 20 active-duty Army brigades.

“That would be a massive buildup, to the tune of probably 100,000 more active-duty Army troops,” a congressional source told The Daily Beast. This could cost the Army somewhere around $17 billion more per year, the source estimated.

Between 2001 and 2009, the Army grew by 72,000 soldiers and spending on Army pay rose over $30 billion, said Chris Preble, vice president for defense and foreign policy studies at The Cato Institute. This provides one way to measure how much it would cost in pay and benefits alone to build that many new brigades.

And if the economy is doing well, as Fiorina promised it will with her as president, it becomes more difficult for the Army to recruit new soldiers.

“The military has to pay more, and offer more, to incentive people to join,” Preble said.

Meanwhile, the Marines are on track to have a total of 32 infantry battalions by the end of fiscal year 2017: 24 active-duty and eight in the Marine Reserves.

If Fiorina was talking about active-duty battalions, her plan would add 12 more battalions, or roughly 12,000 more Marines—a significant buildup. However, if she was talking total infantry battalions—active-duty and Reserves included—her plan would only add four.

Without knowing more, it’s difficult to put a price tag on this part of her defense plan.

By giving a range of 300 to 350 ships in her hypothetical Navy, Fiorina has also left a lot of wiggle room in her naval plans.

The Navy’s current 30-year shipbuilding plan falls somewhere in the middle of her range.

The Navy is on track to reach 321 ships by fiscal year 2028 but then stabilize just around 306, said Todd Harrison, the director of defense budget analysis at the Center for Strategic and International Studies.

The ship count in next year’s budget is 282.

The Navy should hit the 300-ship mark around 2020. To reach 350 ships over that same time period would require the service to either stop retiring ships, which take more people to man them, or build new ones, the congressional source said. To build that over the same period would probably mean doubling the shipbuilding budget from roughly $15 billion a year to $30 billion, he said.

Already, Congress has concerns about the affordability of the Navy’s current plans.

“It has been known for some time that implementing the 30-year shipbuilding plan would require shipbuilding budgets in coming years that are considerably greater than those of recent years,” an August Congressional Research Service report said.

Without more details about what kind of ships Fiorina would buy, it’s difficult to come up with a cost estimate for her proposal.

“Throwing around ‘XX number of ships’ as though it were a meaningful metric signals that someone really hasn’t given it much thought,” Preble said.

This gets to a larger and more important question, he added. “What are the additional soldiers, Marines, and Navy ships for?”

More troops could possibly deploy to Eastern Europe to deter Putin, as Fiorina suggested Wednesday. Or U.S. ground troops could deploy to Iraq and Syria to directly take on the Islamic State. But neither of these missions—as currently discussed by Republican presidential candidates—would constitute a major war that would require such a military buildup.

As for Fiorina’s proposed overhaul of the country’s nuclear arsenal, it is already scheduled for major upgrades over the next 10 to 15 years. The only problem is no one—including top Pentagon officials—knows where the money is going to come from to pay for it all.

The United States maintains what’s called a nuclear triad, or three different ways to carry nuclear weapons: intercontinental ballistic missiles, submarine-launched ballistic missiles, and bomber aircraft that can drop nuclear warheads. All three of these are scheduled for major upgrades over the coming years.

A January study from the Congressional Budget Office estimated the Pentagon would spend $348 billion on its nuclear weapons plans between 2015 and 2024. The Pentagon and the Department of Energy are still hammering out the details for what it can actually afford, but current plans require the annual nuclear weapons budget to double over the next several years, eventually eating up somewhere between 6 and 10 percent of the overall defense budget.

When it comes to Navy ships and upgrading the country’s nuclear weapons, “I think her proposals are roughly in line with what the Obama administration is already doing,” Harrison said.

“The bottom line is it will take many years to grow the Navy and modernize nuclear forces—longer than the four or eight years the next administration will be in office,” he added.