US bunker bombs on Yemen put Iran, China and N Korea on notice – Asia Times

In a high-stakes show of force, the US has dropped bunker-buster bombs on underground weapons depots in Yemen, the latest sign that the Gaza war is spreading across the wider region.

This month, multiple media outlets reported that the US deployed B-2 Spirit stealth bombers to strike underground weapons storage facilities controlled by Yemen’s Iran-backed Houthi rebels, marking the US’s first use of the bomber in the region.

The B-2s reportedly dropped GBU-57 Massive Ordnance Penetrator (MOP)/B bunker-buster bombs on five bunkers housing weapons used in attacks on vessels in the Red Sea.

US Defense Secretary Lloyd Austin described the strike as a demonstration of the US’s ability to target deeply buried and fortified sites, emphasizing that it was authorized by US President Joe Biden to degrade the Houthis’ capability.

The Houthis, who have attacked over 80 vessels since October 2023, have intensified their missile and drone strikes in response to the Gaza conflict, including actions against Israeli and US assets.

The strike also served as an indirect warning to Iran, a key Houthi ally, given its ongoing tensions with Israel and the US. Despite the sophisticated nature of the operation, no immediate civilian casualties were reported.

While details about the GBU-57 MOP/B remain classified, Global Security mentions that the munition is a powerful, precision-guided bomb weighing nearly 13,600 kilograms and containing over 2,400 kilograms of explosives that is designed to penetrate deeply buried targets.

Global Security says GPS-aided Inertial Navigation System (INS) guides the bomb, which can be deployed from B-52 and B-2 bombers and can breach 61 meters of 34.5 megapascal (MPa) reinforced concrete or 38 meters of moderately hard rock.

As for the nature of the targets destroyed in the strike, Ian Williams and Shaan Shaikh mention in a June 2020 Missile Threat report that Houthi rebels have developed sophisticated underground facilities to conceal and protect their missile launchers, making them harder to detect and destroy.

Williams and Shaikh note that these underground sites are used to store and launch ballistic missiles, which have been employed to strike Saudi Arabian targets and disrupt Red Sea shipping.

They say Houthi media frequently showcases these hidden missile sites, highlighting their ability to evade aerial surveillance. In addition, they state that the tactic, combined with the use of drones for reconnaissance, allows the Houthis to maintain a resilient missile capability despite coalition airstrikes targeting their missile arsenals and launch points.

Further, the Houthi’s use of tunnel warfare presents multiple challenges even to technologically advanced forces such as the US.

In an August 2023 article in the peer-reviewed Studies in Conflict and Terrorism journal, Daphné Richemond-Barak and Stefan Voiculescu-Holvad mention that tunnel networks undermine modern precision warfare at the strategic level. They say destroying tunnel networks requires massive resources for detection and neutralization, often resulting in high collateral damage and limited long-term impact.

Despite those challenges, the US use of B-2s with MOP bombs in Yemen may hint at its concept of conventional deterrence.

In a 2018 article for Strategic Studies Quarterly, Robert Haffa Jr mentions that conventional deterrence focuses on preventing aggression through the credible use of advanced conventional military capabilities, with the essential components of capability, credibility and communication remaining crucial.

Haffa Jr argues that conventional deterrence requires visible, swift and decisive forces backed by advanced technologies like precision munitions, stealth and cyber capabilities and succeeds by making aggression costly and futile.

In line with Haffa’s concept, the B-2 strikes using MOP bombs on the Houthis demonstrate the US’s ability to conduct long-range precision strikes against fortified targets, showcasing that adversaries with significant defenses are still vulnerable to US firepower.

While Iran’s hidden nuclear facilities have been identified as potential targets for US or Israeli bunker-busting strikes, its underground missile and air bases may also be targeted for such attacks.

In February 2023, Asia Times reported on Iran’s unveiling of the Oghab-44 underground air base, marking a significant enhancement in its military capabilities, particularly for maritime precision strikes in the Persian Gulf.

Oghab-44, located northeast of Bandar Abbas, protects Iran’s aging pre-1979 aircraft, including F-4 Phantoms, from pre-emptive strikes. Equipped with critical facilities, it supports Iran’s asymmetric anti-access/area-denial (A2/AD) strategy, enabling surprise strikes and precision retaliation against US naval forces in the Persian Gulf.

Beyond the Middle East, the US’s use of B-2 bombers to drop MOP bombs also sends a clear message to North Korea and may concern China about its submarine base in Hainan opening onto the South China Sea.

In a 2024 two-part Beyond Parallel report, Joseph Bermudez Jr and other writers mention that North Korea continues to enhance its missile capabilities through its network of underground facilities (UGF), which are crucial for concealing and protecting its ballistic missile systems.

Bermudez Jr and others highlight ongoing construction at the Hoejung-ri Missile Operating Base near the Chinese border, including a new building adjacent to an underground missile facility. They note that this base and others like Goal and Kumchon-ni form part of North Korea’s strategic missile belt.

In a separate November 2018 Beyond Parallel report, Bermudez Jr and other writers mention North Korea deploys its missiles at three belt locations: strategic, operational and tactical, based on their distance from the Demilitarized Zone (DMZ).

North Korea’s strategic missile belt is more than 150 kilometers north of the DMZ. It was initially equipped with Nodong missiles and likely houses newer Hwasong missiles. The operational belt is 90-150 kilometers north of the DMZ and equipped with Nodong medium-range ballistic missiles or longer-range systems.

Finally, the tactical belt, located 50-90 kilometers north of the DMZ, is equipped with Scud short-range ballistic missiles (SRBM) and covers critical facilities in northern South Korea.

As for China, CNN reported in August 2020 that satellite imagery revealed a Chinese Type 093 nuclear-powered attack submarine (SSN) entering an underground base on Hainan Island’s Yulin Naval Base.

CNN mentions this rare sighting underscores China’s strategic use of underground facilities to conceal military assets, enhance operational security and complicate adversary surveillance.

However, even a conventional attack on North Korea’s missile forces and China’s undersea nuclear deterrent, despite its “no-first-use”  nuclear policy, may still prompt a nuclear response from both potential US adversaries.