It's now GOP policy to build a US Iron Dome. Here's what Trump's plan could mean.

As Republicans look toward their party convention in Milwaukee next week, the new Donald Trump-style approach to national security represents a dramatic departure from the GOP's past.

Eight years ago, the party called for a military large enough to fight more than two major wars at once and wanted tougher sanctions against Russia. Now, the new 2024 GOP platform talks of avoiding conflict because "wars breed inflation."

Official GOP policy also calls for a American-built national missile defense system similar to Israel's Iron Dome – something the military hasn't asked for and experts say could have limited utility for the United States.

"PREVENT WORLD WAR THREE, RESTORE PEACE IN EUROPE AND IN THE MIDDLE EAST, AND BUILD A GREAT IRON DOME MISSILE DEFENSE SHIELD OVER OUR ENTIRE COUNTRY -- ALL MADE IN AMERICA," the 2024 GOP platform states of the party's new goals.

So, where did this talk of a U.S. Iron Dome come from? And is it even realistic?

Here's what to know:

Trump wants 'the greatest dome of them all'

Iron Dome was developed by Israel to zap rockets and mortar fire out of the sky -- acting as a kind of shield over a country under the near-constant threat of short-range and medium-range missile attacks.

The multi-billion system played a major role in successfully defending Israel last April when Iran launched some 300 missiles and drones at the Jewish state in retaliation for an Israeli airstrike that killed a top Iranian commander.

Iron Dome's success caught the attention of Trump, who had already been tossing out the idea at campaign rallies that the U.S. could build its own version of the technology considering the U.S. had spent some $3 billion to help Israel manufacture and maintain the system.

Trump's comments on a U.S. Iron Dome often prompted loud cheers from his supporters, much as it had in 2016 when he called for building a wall at the U.S. southern border with Mexico.

"In my next term, we will build a great Iron Dome over our country, a dome like has never seen before, a state -of-the-art missile defense shield that will be entirely built in America," Trump said at a June rally in Wisconsin as the crowd applauded.

"We're going to build the greatest dome of them all," he promised.

The military hasn't asked for an Iron Dome, and it wouldn't protect against the latest threats anyway

On its surface, experts say replicating an Iron Dome system for the U.S. wouldn't make much sense. With allies north and south of the U.S., and oceans on either side, the U.S. doesn't face the same kind of short-range missile threat as Israel.

But what about a nation-wide missile defense system that's like the Iron Dome but tailored for the U.S.?

According to a U.S. defense official, U.S. Northern Command -- the military combatant command charged with defending the homeland from foreign missiles -- has not expressed interest in a nationwide missile defense system.

The military already employs multiple systems "that together provide agility in responding to potential threats, which increases available options for the nation's leaders," said the official, who spoke on condition of anonymity.

Among those systems is Ground-Based Midcourse Defense program, which was designed to knock down rogue long-range missiles from a country like North Korea. It would, however, have more limited utility if there were ever a large-scale attack from a country with a hefty arsenal like Russia.

Expanding that system to cover every inch of the U.S. though would likely cost billions of dollars at a time when the country also is trying to protect against attacks in cyber and space. China and Russia are now pursing hypersonic weapons, while administration officials this spring acknowledged Russia's pursuit of nuclear capabilities in space, greatly complicating what it means for any one system to keep the U.S. safe.

"You can't defend the entire United States. It's unrealistic, unaffordable and unachievable," said Gen. Glen VanHerck, who retired this year as head of U..S Northern Command and North American Aerospace Defense Command.

Instead, he said, whoever is in the White House next year should develop clearer policy on what U.S. assets to defend beyond critical military infrastructure -- something he said he pressed for during his tenure as head of NORTHCOM.

"Ultimately, it goes back to policy. What are your priorities? What do you want us to do? And then we can make realistic decisions with the force we have today, and we can then budget and resource for the forces of the future," he said.

Just like his border wall, Trump's calls for a US Iron Dome is likely shorthand for something else

Party platforms and campaign rhetoric tend to be more political crowd-pleasers than pragmatic blueprints for how to run a country.

In 2016, for example, Trump called for a "big, beautiful" wall along America's southern border with Mexico; when he left office, only about a quarter of the border had new fencing -- most of which replaced smaller existing structures. Trump's demands for a border wall were essentially shorthand for hardline immigration policies.

Military analyst Steve Ganyard, a retired Marine Corps colonel and an ABC contributor, said calling for an Iron Dome over the U.S. probably doesn't make much sense from a strategic standpoint considering the new threats from space. More notable, he said, is what's missing from the document.

For the first time in decades, the party isn't calling for increased spending for a bigger fighting force or extending U.S. military reach globally.

"It just strikes me as how isolationist it is, particularly in comparison to past Republican platforms," Ganyard said.

For former Trump advisers, refocusing US spending on homeland security is a good thing.

"It's a very strong document that has sound common-sense principles that include building up the American military base," Elbridge Colby, who served as deputy assistant secretary of defense for strategy and force development during the Trump administration, said of the new GOP platform.

The platform forces on protecting the homeland, "not looking for monsters to destroy," Colby said.