Forget the U.S. Navy aircraft carrier that President Donald Trump claimed, wrongly, was steaming toward North Korea to punish Kim Jong Un’s regime for apparently testing a nuclear-capable ballistic missile last Saturday.

Forget the U.S. Marine Corps F-35 stealth fighters that practiced bombing runs on the Korean Peninsula in late March. Forget the contingent of U.S. Army soldiers—part of the 29,000-strong American ground force in South Korea—that Vice President Mike Pence visited Sunday, just a day after Pyongyang’s latest missile test failed.

No, if the United States seriously intends to punish North Korea for continuing to develop nuclear warheads and the rockets to deliver them, then the punitive blow will likely come from Missouri.

That is, in the form of stealth bombers carrying America’s biggest non-nuclear bombs.

Not the 11-ton Massive Ordnance Air Blast (MOAB) fuel-air bomb that U.S. forces dropped on suspected ISIS positions in eastern Afghanistan on April 13. Rather, an even bigger munition.

Since the 1990s, the U.S. government has been preparing to attack North Korea’s most heavily protected military facilities, specifically in order to slow or halt Pyongyang’s nuclear program.

The American plan involves long-range, radar-evading stealth bombers hauling gigantic, earth-penetrating bombs. The scheme began in the mid-1990s, as President Bill Clinton and hawkish Republican lawmakers sparred over a nascent nuclear pact with the reclusive North Korean regime.

The plan advanced further in the early 2000s under President George W. Bush’s policy of pre-emptive military strikes—the same policy that mired the United States in Iraq for, so far, 14 years of grinding warfare.

In the early 1990s, North Korea was not yet a nuclear power—but it certainly possessed the potential to become one. The Clinton administration aimed to head off Pyongyang’s atomic ambitions and by some accounts an attack was imminent, at the risk of an enormous casualty count, until former President Jimmy Carter stepped in and offered another remedy by diplomatic means.

In early 1994, the U.S. State Department signed the “Agreed Framework” with North Korea. The deal was simple. Pyongyang would suspend development of weapons-grade nuclear reactors if, in exchange, Washington helped the impoverished country build nuclear reactors that weren’t weapons-grade.

The Bush administration labeled the framework “appeasement” and, by 2004, had abandoned it.

Two years later, North Korea triggered its first nuclear test blast.

Under Bush and Vice President Dick Cheney, the Pentagon hewed to a policy of preemption. In November 2001, just a few weeks after the 9/11 terror attacks, Cheney announced that if there was even a 1 percent chance that a threat was real, “we have to treat it as a certainty in terms of our response.”

Cheney’s 1-percent doctrine drove the United States to war with Iraq over that country’s purported—and to this day unsubstantiated—efforts to field weapons of mass destruction. The doctrine shaped America’s approach to North Korea, as well.

In mid-2002, Secretary of Defense Donald Rumsfeld directed the Pentagon to rewrite its plan for war with North Korea—OPLAN 5027—to allow for preemptive air raids on Pyongyang’s nuclear facilities.

But the North Korean regime had been busily burying its most important military sites. Starting in the 1960s, Pyongyang constructed as many as 8,000 underground facilities, Maj. Park Sung-man, a South Korean military officer, told wire service UPI in 2015. Park claimed he got those numbers from a U.S. source.

Under Bush, the U.S. armed forces lacked the means to destroy the deepest facilities. During the 1991 Gulf War, the military had rushed production of 5,000-pound bunker-busting bombs capable of punching through 100 feet of earth or 20 feet or concrete. A few years later, the Pentagon developed 2,000-pound bombs that it concluded were 25 percent more effective against underground sites. More than a decade later, these two munitions remained America’s best weapons for destroying North Korea’s underground military infrastructure.

They weren’t enough.

“Neutralization of an underground facility... is a formidable task,” Air Force Col. Russell Hart wrote in a 2012 paper. To collapse the most “hardened” subterranean facilities, the Defense Department determined that it would need to skip a 10- to 15-ton bomb into a tunnel entrance in order to blow through the door and send a shock wave into the site.

The Bush administration considered fielding a “Robust Nuclear Earth Penetrator”—in essence, a tactical nuclear weapon with a harder-than-usual shell that could burrow deeper into the ground than other atomic bombs. The Union of Concerned Scientists concluded that the RNEP could “produce tremendous radioactive fallout.”

Congress balked at preemptively nuking North Korea’s nukes. Lawmakers wanted a non-nuclear alternative. In 2004, the Pentagon began development of the Massive Ordnance Penetrator, a 15-ton conventional bomb specifically designed to collapse all but the deepest buried facilities in Iran and North Korea.

MOP was ready for combat in 2011. Each of the Air Force’s 20 B-2 stealth bombers based at Whiteman Air Force Base in Missouri can carry two of the 21-foot-long munitions. So, forget carriers, stealth fighters, and ground troops. The B-2s and the massive bombs are, at present, America’s only non-nuclear options for destroying Pyongyang’s best-protected weapons sites.

Also ignore Trump when he threatens to send a naval armada toward Pyongyang. Disregard Pence as he inspects Army formations along the Korean Demilitarized Zone. If you want to know if, and when, the United States intends to attack North Korea, look to Missouri—and stealth bombers hauling massive, ground-penetrating bombs.