America’s Newest Bunker Buster Just Entered Combat for the First Time

On March 17, US Central Command confirmed that multiple 5,000-pound deep penetrator munitions were used against hardened Iranian missile sites along the coastline near the Strait of Hormuz. Pentagon officials subsequently confirmed the weapon was the GBU-72/B Advanced 5K Penetrator, marking its first use in combat. The sites targeted were housing anti-ship cruise missiles threatening commercial shipping through the strait.

What the GBU-72 Is

The GBU-72 Advanced 5K Penetrator is a 5,000-pound bunker-buster designed to replace the GBU-28, which has been in service since 1991. It was first tested in 2021, with initial tests validating that a modified 2,000-pound JDAM tail kit could successfully navigate and control a weapon nearly three times its original design weight. The weapon was built specifically to address deeply buried hardened structures that existing munitions cannot reliably penetrate.

The Air Force developed the GBU-72 using advanced modeling and simulation before producing the first physical warhead. According to GBU-72 Program Manager James Culliton, that approach allowed early prototypes to closely resemble final production models and enabled operational test partners to validate designs and procedures earlier than traditional development timelines allowed. Culliton described the weapon’s expected lethality as significantly higher than the GBU-28 it replaces.

The Platforms That Can Carry It

Only two aircraft have been publicly cleared to employ the GBU-72: the B-1B Lancer and the F-15E Strike Eagle. The weapon was first tested on the Strike Eagle in 2021. Photographs of B-1B external carriage testing emerged in 2024, with Air Force video footage confirming testing on the bomber’s external Load Adaptable Modular pylons in 2025.

The payload difference between the two platforms is significant. The F-15E is likely limited to a single GBU-72 on its centerline station without sacrificing external fuel tanks. Unconfirmed reports indicate the B-1B can carry up to 12 of the weapons, making it substantially more effective for large-scale hardened target strikes.

What the Evidence Suggests

CENTCOM did not specify which aircraft conducted the March 17 strikes. Flight tracking data showed two B-1Bs operating from RAF Fairford on that date, tracked over the eastern Mediterranean at approximately 1:30 pm UTC outbound toward Iran and 10:20 pm UTC returning to the UK, timing consistent with CENTCOM’s statement. One of two recorded B-1B missions that day aborted due to unspecified issues. The other proceeded to target.

F-15E Strike Eagles deployed within CENTCOM’s area of responsibility could also have conducted the strikes from much closer locations, making them significantly harder for open-source analysts to track. Privacy screens have been positioned along RAF Fairford’s perimeter fences in recent weeks, preventing observers from documenting B-1B operations and weapons loading.

The GBU-72 joins a lineup of penetrating munitions already extensively used in Iran including the GBU-31(V)3 JDAM bunker-buster variant, AGM-158 JASSMs, and ship-launched Tomahawk cruise missiles. The introduction of the GBU-72 against Iranian coastal missile infrastructure represents a meaningful escalation in the weight of ordnance being applied to hardened targets.