Two weeks ago we noticed something quite "persuasive": ahead of the culmination of the March 31 April 2 Iran nuclear negotiations, the US had dispatched a huge naval presence to the Persian Gulf as part of "Eagle Resolve" a military exercise held in plain view of the Iranian coastline. The massive operation would consist of tactical exercises from the US Army, Marines, and various other military branches "with simulated portions of the exercise based on a fictional adversary." Just in case the intention of this wargame was not clear, a CENTCOM official was quick to point out that "the exercise is not intended as a signal to Iran." Iran quickly got the "non-signal" message and a few days later agreed to a preemptive agreement with John Kerry which has since been revealed, is anything but a "nuclear deal."

So as the world awaits the outcome of next Iran "deadline"- the June 30 conclusion of the finalization of the Iran deal - the US is already hedging its bets. According to the WSJ, the Pentagon has "upgraded and tested the largest bunker-buster bomb in the U.S. arsenal, senior U.S. officials said, readying a weapon that could destroy or disable Iran’s most heavily fortified nuclear facilities should a nuclear deal fall apart and the White House decide to take military action."

It turns out as the Nobel peace prize winner and his henchmen were talking peace, the Pentagon is actively preparing for war:

Even while the Obama administration was pursuing a diplomatic agreement with Iran to rein in its nuclear program, the Pentagon was readying the improvements to one of its most destructive conventional weapons, including electronic countermeasures to prevent an adversary from jamming its guidance systems. “The Pentagon continues to be focused on being able to provide military options for Iran if needed,” a senior U.S. official said. “We have not taken our eyes off the ball.”

As noted previously, U.S. officials are unsure whether the terms of a final accord can be reached before a June 30 deadline. "Officials said major gaps remained over the technical details as well as implementation, and it is unclear if the U.S. Congress will pass legislation challenging the White House’s terms."

So, just to make sure there is no negotiating stumbling blocks on behalf of Tehran, the US is doing its best to "negotiate" with a gun to Iran's head. Or, as the case may be, a Massive Ordnance Penetrator, aka MOP.

A brief history of the GBU-57:

This is what the GBU-57 MOP looks like to scale:

Here is the MOP locked and loaded:

How the MOP is said to work:

Back in 2012, the WSJ reported that the previous iteration of the 30,000-pound (13,607 kg) bunker buster wasn’t powerful enough to destroy some fortified Iranian nuclear facilities. So work began to upgrade the bomb’s design and guidance systems. That upgrade is now complete.

The Pentagon declined to comment on any improvements to the so-called Massive Ordnance Penetrator, or MOP. “The United States military prepares for a broad range of potential threats to include developing munitions designed to address deeply buried and hardened facilities,” said Col. Steve Warren, a Pentagon spokesman.

The redesigned bunker-buster is clearly intended to be unleashed on Iran's mountainous research facilities in a worst case scenario:

The Pentagon designed the bunker buster with heavily fortified sites—including Iran’s Fordow installation—in mind. Fordow is built into a mountain to protect the facility from U.S. or Israeli airstrikes. To destroy or disable the underground facilities, the Pentagon envisages guiding two or more of the bunker busters to the same impact point, in sequence, extending the weapon’s burrowing power, the officials said.

The MOP is so strong, the WSJ compares its destructive force to a nuclear weapon:

Those upgraded electronic countermeasures, combined with improvements to the weapon’s guidance systems, will allow the weapon to be targeted with a precision previously possible only for far smaller guided bombs in the U.S. arsenal, the officials said. Steering two or more massive ordnance penetrators to a single entry point would have a devastating effect never before seen by a nonnuclear weapon, the officials said. The White House has repeatedly said that Mr. Obama will need to look at other options if the nuclear talks break down. “If you say all options are on the table, you have to have something on the table that’s credible,” a senior U.S. official said.

What remains unknown is whether Israel is also in possession of the MOP, because while theatrical politics at the top echelons of power suggest a breakdown in US-Israel relations, it is behind the scenes where the real action takes place:

The U.S. has balked at providing its biggest bunker buster bomb to Israel, but Pentagon officials have shared details about its capabilities with their Israeli counterparts, and has shown them videos of the weapon hitting a target during testing. In one of those videos, which was described by U.S. officials who have viewed it, a massive ordnance penetrator is seen dropping in slow motion toward a large “X” marking the target at an undisclosed test site. The video then cuts to an image showing an underground bunker buried beneath the “X” and depicts the site’s destruction.

In other words, US officials are just waiting for the right Israeli offer.

As for the question whether the MOP will be actually used, which is basically a question whether the Iran "deal" will fall apart over the next three months, ask Boeing - the maker of the GBU-57 MOP - which stands to benefit (or lose) the most from any war (or lack thereof) with Iran.

And just to make sure the outcome is one in which the most blood is shed...

Source: Open Secrets