For all of the debate and politicking surrounding the Iran nuclear deal, there does seem to be consensus on one question — the absence of a deal increases the likelihood of military conflict with Iran. Walking away from a deal negotiated in good faith with America’s allies would, by many accounts, make it difficult to find a peaceful, diplomatic solution to the Iranian nuclear problem.

Crippling economic sanctions have been a popular weapon by the international community to discourage Iran from obtaining a nuclear weapon. The prospect of removing those sanctions supplied the leverage with Iran for U.S. President Barack Obama’s administration to broker its nuclear deal. The Obama administration has emphasized provisions of the deal that allow the sanctions to “snap back” amid evidence of a nefarious nuclear activity on the part of the Iranians.

But there’s a much bigger weapon in the American arsenal that could be used to stop Iran’s development of a nuclear weapon. It’s a 30,000-pound bomb. Such a weapon would be necessary to penetrate Iran’s enrichment facility at Fordo.This nuclear enrichment facility was a closely kept secret by the Iranians until satellite imagery shed light on it in 2009. This facility is built deep inside a mountain in order to make it impenetrable to airstrikes, as the Iranians presumably knew any nuclear weapons program would be targeted militarily by the international community.

But Fordo is not completely impenetrable. There is one nation that possesses one weapon with the capacity to crack the mountain facility.

That nation is the United States of America. That weapon is the massive ordnance penetrator. At 30,000 pounds, it is six times the size of the largest bunker-busting bombs that existed prior to its development. It’s more than 20 feet long, nearly 3 feet wide, and delivers a 5,000-pound warhead.

This is the trump card to keep Iran honest in the nuclear deal. Secretary of Defense Ashton Carter alluded to this in his testimony to the Senate Armed Services Committee on July 29. Carter noted that the proposed agreement places no limitations on the Department of Defense, leaving American military might as an unfettered option to prevent Iran from getting a nuclear bomb.

“It places no limits on our forces, our partnerships and alliances, our intensive and ongoing security cooperation, or on our development and fielding of new military capabilities — capabilities we will continue to advance,” Carter said of the Iran deal.

Speaking of advancing capabilities, the massive ordnance penetrator is so large it can only be dropped by the United States’ massive strategic long-range bombers, the B-52 Stratofortress, and the B-2 Spirit. Even if the United States didn’t have the only military with the massive ordnance penetrator, it is the only country that could use it.

The weapon is capable of penetrating several dozen feet of concrete before detonating deep underground with a, well, massive explosion. The impressiveness of the weapon can be seen below. Note its ability to penetrate cement before detonating in a massive explosion.

If the multi-national agreement to disarm the Iranian nuclear program goes through, but Iran reneges on the deal and attempts to procure or produce weaponized nuclear material, it well could necessitate military action. The deal requires Iran to repurpose its mountain facility at Fordo for research, and to allow international scientists to have open access to it. If the Iranian regime were to violate that and attempt to produce nuclear material for a weapons program; the Fordo facility, or a similarly bunkered one; would have to factor heavily in that plan to avert an airstrike. Hence why the massive ordnance penetrator is such a vital weapon.

The ability of the United States to strike the Fordo facility was highlighted in an interview between former Director of the CIA and retired Army Gen. David Petraeus with the Atlantic’s Jeffrey Goldberg at the Aspen Ideas Festival earlier this month.

Petraeus has been a constructive critic of a deal with Iran, partnering with a bipartisan commission, including several former Obama administration national security officials, to pen a letter earlier this summer outlining provisions he believed needed to be satisfied in order for a deal to be good.

In Aspen, Goldberg asked Petraeus if he believed Obama could take military action against Iran.

“I think it’s inevitable if there is incontrovertible evidence that they are moving to make a bomb. That’s our president’s policy,” Petraeus replied. “That was very deliberately thought through, announced a number of different occasions, and I think it would be a mistake for Iran to think that’s not a reality.”

Seeming a bit surprised, Goldberg asked, “So you believe that President Obama would still under certain circumstances use military force against Iran?”

“I think he would, actually,” Petraeus responded, while admitting the president has broken diplomatic “red lines” in the past — presumably referring to the U.S.’s failure to take military action against Syrian President Bashar al Assad in 2013 after his government appeared to use chemical weapons against children and other civilians. “I think this is a different issue.”

Here’s where it gets interesting. Goldberg asked Petraeus about the role Israel would play in militarily confronting Iran should the international community find itself in a no-deal scenario.

“How did the [Obama] administration keep Israel from attacking Iran?” Goldberg asked. “And do you think that if this deal does go south … that Israel would be back in the picture?”

“Umm … I don’t, actually,” the former general replied. “I think Israel is very cognizant of its limitations … [U.S. Army Gen. Martin Dempsey] the chairman of the Joint Chiefs in an open hearing did note that the Israelis do not have anything that can crack this deeply buried, hardened enrichment site inside the mountain at Fordo. And if you can’t do that, you’re not going to set the program back all that much.

“That’s a huge limitation. It’s also publicly known that we have a 30,000-pound projectile that no one else has, no one else can even carry,” Petraeus added, referencing the massive ordnance penetrator.

Petraeus explained that the bomb has been in development for years, starting when he was the commander of U.S. Central Command. It is a part of the United States’ plan to take out those Iranian nuclear facilities militarily, if need be.

Petraeus then channeled a maxim on warfare from the the late 19th century German chancellor, Otto von Bismarck.

“But you know, that’s another roll of the iron dice, as Bismarck used to say,” Petraeus said. “And you don’t know what the outcome of those dice are going to be. You don’t know what risks could materialize for those in harm’s way. You don’t know what the response could be from Iran.”