前总统唐纳德·特朗普(Donald Trump)重申了他建造“世界上最好的铁穹”的承诺，这是由美国国防部建造的防空系统的一个版本以色列专家说，对于像加拿大和美国这样有友好邻邦的国家来说，这可能没有多大意义墨西哥.
周一晚上，特朗普在社交媒体平台X上与埃隆·马斯克(Elon Musk)进行了一次对话，他为自己的想法进行了辩护，称“只需要一个疯子，你知道，就可以开始做一些事情。”
“以色列有。我们将拥有世界上最好的铁穹。我们需要它，我们会把它做好，”他告诉马斯克。
让我们看看什么是铁穹，为什么专家质疑它对美国的效用，以及特朗普实际上可能在谈论其他事情:
什么是‘铁穹’?
“铁穹”是由以色列的拉斐尔先进防御系统公司开发的，用于打击短程火箭，如以色列军队从黎巴嫩边境发射的火箭伊朗真主党支持的组织。
与旨在拦截弹道导弹和巡航导弹的大卫吊索(David's Sling)等其他系统一起，以色列的铁穹(Iron Dome)是覆盖该国的全国导弹防御盾的一部分，其居民生活在来自邻国的近乎持续的攻击威胁下。
去年4月，当伊朗发动攻击时，这个价值数十亿美元的系统被认为帮助击落了数百枚导弹和无人机。如果伊朗兑现其再次袭击以色列的威胁，这一次是为了报复最近访问德黑兰的哈马斯领导人被杀，以色列的铁穹将在未来几天发挥重要作用。
根据国会研究服务中心(Congressional Research Service)最近的一项分析，作为帮助保护以色列的更广泛政策的一部分，美国迄今已向以色列支付了约30亿美元的铁穹电池、拦截器和维护费用。
美国能从自己的“铁穹”中获益吗?
专家的简短回答大概是不会。美国的盟友位于美国的北部和南部，两边都是海洋，因此美国不像以色列那样面临短程导弹的威胁。
这一现实可能解释了为什么军方没有要求国会出资建造一个。一名美国国防官员上个月告诉美国广播公司新闻，美国北方司令部也没有对更大的全国性导弹防御系统表示兴趣。北方司令部是负责保卫国土免受外国导弹袭击的军事作战司令部。
这位不愿透露姓名的官员在7月份表示，军方已经采用了多个系统，“这些系统共同提供了应对潜在威胁的灵活性，增加了国家领导人的可用选择”。
美国已经部署的系统中包括地基中段防御计划，该计划旨在打击来自朝鲜等国家的远程导弹。美国有可能试图增强现有系统的能力，以消除来自一个拥有庞大核武库的国家的任何大规模攻击威胁俄罗斯.
但是，在这个国家还试图防范网络和空间攻击的时候，将该系统扩展到美国的每一寸土地可能会花费数十亿美元。中国和俄罗斯现在正在寻求高超音速武器，而政府官员今年春天承认俄罗斯在太空中寻求核能力，这使得任何一个系统保持美国安全的意义都变得非常复杂。
那么，为什么特朗普一直在谈论建立一个铁穹呢?
特朗普经常坚持为国家建设东西的想法，因为这是政策理念的一个切实例子。
在2016年的情况下，特朗普谈到修建边境墙，以此表示他将严肃对待非法移民，尽管专家警告说这一想法不切实际。到特朗普离任时，只有大约四分之一的美国与墨西哥边境有新的围栏，其中大部分取代了较小的现有结构。
在铁穹的情况下，特朗普似乎发出了美国政策的另一个转变信号——远离与其他国家的外交接触，支持依赖巨额军费开支来威慑对手的孤立主义政策。
就其本身而言，共和党将这一想法作为其官方政策平台的一部分在7月的共和党大会上。
在特朗普政府期间担任负责战略和部队发展的副助理国防部长埃尔布里奇·科尔比(Elbridge Colby)去年7月表示，他认为新的共和党平台是一种有意的转变。
科尔比说，共和党专注于保护家园，“而不是寻找怪物来摧毁”。
Trump wants a US 'Iron Dome' the military hasn't asked for
Former President Donald Trump is reviving his promise to build "the best Iron Dome in the world," a version of the air defense system built byIsraelthat experts say probably wouldn't make much sense for a country with friendly neighbors like Canada andMexico.
In a conversation Monday night with Elon Musk on his social media platform X, Trump defended his idea by saying "it just takes one maniac to, you know, start something."
"Israel has it. We're gonna have the best Iron Dome in the world. We need it, and we're gonna make it all," he told Musk.
Here's a look at what Iron Dome is, why experts question its utility for the U.S. and how Trump might actually be talking about something else:
What is an 'Iron Dome'?
Iron Dome was developed by Israel's Rafael Advanced Defense Systems to knock down short-range rockets, such as the ones lobbed from the border of Lebanon by theIran-backed group Hezbollah.
Together with other systems like David's Sling, which is designed to intercept ballistic and cruise missiles, Israel's Iron Dome is part of a nationwide missile-defense shield over the country, whose residents live under the near-constant threat of attack from its neighbors.
The multi-billion dollar system was credited with helping to knock down hundreds of missiles and drones last April when Iran launched an attack. Israel's Iron Dome could play a major role in coming days if Iran follows through on its threat to attack Israel again, this time in retaliation for the recent killing of a Hamas leader visiting Tehran.
As part of a broader policy to help defend Israel, the U.S. has paid some $3 billion to Israel to date for Iron Dome batteries, interceptors and maintenance costs, according to a recent analysis by the Congressional Research Service.
Could the US benefit from its own 'Iron Dome'?
The short answer from experts is probably not. 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.
That reality probably explains why the military hasn't asked Congress to pay to build one. A U.S. defense official told ABC News last month that U.S. Northern Command -- -- the military combatant command charged with defending the homeland from foreign missiles -- has not expressed interest in a larger, nationwide missile defense system either.
The military already employs multiple systems "that together provide agility in responding to potential threats, which increases available options for the nation's leaders," the official, who spoke on condition of anonymity, said in July.
Among those systems already in place in the U.S. is the Ground-Based Midcourse Defense program, which was designed to knock down rogue long-range missiles from a country like North Korea. It's possible the U.S. could try to bolster the capability of this existing system to wipe out any threat of a large-scale attack from a country with a hefty arsenal likeRussia.
But 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.
So why does Trump keep talking about building an Iron Dome?
Trump often latches on to the idea of building things for the country because it's a tangible example of a policy idea.
In the case of 2016, Trump talked about building a border wall as a way of saying he would take illegal immigration seriously, even as experts warned the idea wasn't practical. By the time Trump left office, only about a quarter of the U.S. border with Mexico had new fencing -- most of which replaced smaller existing structures.
In the case of an Iron Dome, Trump seems to be signaling another shift in U.S. policy -- away from diplomatic engagements with other countries in favor of isolationist policies that rely on heavy military spending to deter adversaries.
For its part,the GOP endorsed the idea as part of its official policy platformat the Republican convention in July.
Elbridge Colby, who served as deputy assistant secretary of defense for strategy and force development during the Trump administration, said last July that he saw the new GOP platform as an intentional shift.
The GOP focuses on protecting the homeland, "not looking for monsters to destroy," Colby said.
