America and Iran: big bombs, base politics

The United States air force’s sophisticated new “bunker-buster” weapon could become a critical factor in any escalation of tension over Iran’s nuclear programme.
Paul Rogers author pic
Paul Rogers
22 October 2009

The United States department of defence has confirmed that it is rushing into production the world’s largest ever bomb, one designed specifically to destroy underground targets. The Massive Ordnance Penetrator (MOP) weighs just short of fifteen tonnes, more than 80% of which is made up of a massively hardened ferro-cobalt alloy casing. When dropped from high altitude, the bomb will drive through earth and concrete before two-and-a-half tonnes of explosive are detonated to destroy the target (see “U.S. ‘Bunker Buster’ Bomb ready Soon: Pentagon”, Agence France Presse/Defense News, 8 October 2009).

The Pentagon’s sense of timing here - and those of its political masters - is acute. This, after all, is a moment when the United States is deeply troubled by the conflicts in Afghanistan and Pakistan, facing continuing difficulties in Iraq, concerned about North Korea; and when military specialists are playing a prominent role in advising Barack Obama’s administration over the next phase of its strategy (see “AfPak: the unwinnable war”, 15 October 2009). But in particular, it is the continuing tension between the US and Iran over Tehran’s nuclear plans that makes the arrival of the new weapon a significant political as well as technological event (see Mariano Aguirre, “Barack Obama, Iran, and the nuclear danger”, 20 October 2009).

The growth path

The new weapon, more than ten times as powerful as the current BLU-109 bomb, is planned principally to be delivered from high altitude by the stealth B-2 strategic bomber. It has been under development for some years as a “technology demonstration program”, funded by the Defense Threat Reduction Agency (DTRA); its delivery is a joint project of two of the largest United States arms companies, Boeing and Northrop Grumman (see “The United States, nuclear weapons, and Iran”, 12 January 2006).

The project was until recently believed to be a research programme that would only gradually move to the development stage, but it is now clear that the whole programme has been accelerated and that the first of the new weapons could be deployed within nine months (see “Pentagon eyes accelerated ‘bunker buster’ bomb”, Reuters, 2 August 2009).

The history of weapons of this size began with the “grand slam” bombs of the second world war, but subsequent developments in explosive technology were the basis of the far more powerful bombs developed during the Vietnam war. These could be used to instantly clear rainforest to provide landing-sites for helicopters, as well as against tunnels and other targets. The largest was the 7.5-tonne BLU-82B (“Big Blue”) bomb whose explosive was a mixture of ammonium-nitrate and powdered aluminium with a polystyrene soap binding-agent in aqueous solution. When close to the point of detonation, this produced blast overpressures of up to 1,000 psi (position-specific iterated), close to those of a small tactical nuclear weapon.

These bombs were again used against Iraqi trenches in the January 1991 war following Saddam Hussein’s invasion of Kuwait, and in Afghanistan in late 2001 during the operations against Taliban and al-Qaida paramilitaries in the mountains around Tora Bora. Several journalists who visited areas where the bombs had been dropped reported scenes of extraordinary devastation. These bombs were blast-effect weapons rather than earth-penetrators but were used also to attempt to destroy the entrances to caves (see “The ‘Mother Of All Bombs’ - how the US plans to pulverise Iraq”, 7 March 2003).


In the months before the war to terminate the Saddam Hussein regime was launched in March 2003, reports circulated that a very much larger blast-weapon was being rushed into deployment. Its technical designation was GBU-43/B, its everyday one the Massive Ordnance Air Burst (MOAB) weapon; the latter immediately earned it a name that played on Saddam’s own description of the 1991 war: the “Mother Of All Bombs”. Indeed, it was expected to be used in the war. In the event, the early stages of the war involved rapid manoeuvre warfare and the MOAB wasn’t used, although it remains available for use (see “What happened to the 'Mother Of All Bombs'?”, 3 December 2003).

The MOAB, like its Vietnam-era predecessor, is not specifically designed for destroying underground targets – as a massive blast-weapon it is classed more as an area-impact munition. One of the main differences between it and the earlier “Big Blue” was that that had to be carried by a C-130 Hercules transport aircraft, relatively slow and with limited range. The MOAB, by contrast, was from the start intended to be carried on long-range strategic bombers such as the B-52 and B-2.

In parallel with this type of weapon, there has been intensive research into more sophisticated penetration devices (often referred to as “bunker-busters”). These are designed (as their name suggests) to go through earth, rock or concrete at great speed, driving through many metres of solid material before exploding within underground chambers. The US air force has had these weapons for years, the BLU-109 being the standard system; many such “bunker-busters” have been sold to Israel.

The MOP is set apart by its sheer size and the much more devastating power it contains. Since it can be deployed on the B-2 it would be possible (with air-to-air refuelling) to deploy the weapon to a war-zone in the middle east from Diego Garcia, RAF Fairford in England’s Gloucestershire or, indeed, the B-2’s home base in the United States. The current reports state that a $51.9 million contract has been agreed with Boeing’s McDonnell-Douglas division to modify the bomb bay of the B-2 so that it can carry the MOP. The congressional approval for this move was obtained in August 2009 and the contract let on 2 October.

The development of the new weapon is backed by US Central Command (the unified military system that includes Iraq in its area of operations) and US Pacific Command (whose area includes North Korea). Its core purpose seems clear, though the Pentagon has been careful to avoid any claim that the rush to deployment is connected to Iran’s presumed nuclear-weapons programme. The Pentagon’s press secretary, Geoff Morrell, says:

“I don’t think anyone can divine potential targets or anything of that nature. This is just a capability that we think is necessary given the world we live in these days. The reality is that the world we live in is one in which there are people who seek to build weapons of mass destruction and they seek to do so in a clandestine manner” (see DoD News Briefing…”, Defense News, 7 October 2009).

The clear danger

None of this in itself means that the MOP is likely to be used in combat soon. After all, the weapon also arrives at a time when President Obama is seeking (along with European states and international organisations) to develop a diplomatic dialogue with Iran, in sharp contrast to the policy of the George W Bush administration. There is a sense too in which the new bomb is related to internal competition between different government departments and between the air force and the army. In the latter case, the United States army has been the near-exclusive focus of attention in Iraq and Afghanistan; the air force’s acquisition of this new weapon is a reminder that it too has significant potential to make its mark in the post-9/11 era.

But there are clear dangers in the arrival of a weapon of this size and destructive power, not least if it proves difficult or impossible to negotiate a settlement with Iran. The ambitions and unpredictability of the Mahmoud Ahmadinejad regime, and a regional environment where Israel’s concerns and tensions with Hizbollah have ever-present combustible potential, make such deadlock a real possibility (see “Iran, America, Israel: the nuclear gamble”, 2 October 2009). In the event of continuing deadlock, there would be very heavy pressure on Obama from rightwing sources to take military action - perhaps in the approach to the mid-sessional Senate elections in November 2010. In those circumstances, the United States air force would be only too willing to utilise the new capabilities in its arsenal - including the Massive Ordnance Penetrator. The very existence of this weapon would most certainly add to the pressure on the president.

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