Summary (quick read): Reporting and analysis in recent weeks have focused attention on the GBU-57A/B “Massive Ordnance Penetrator” (MOP) — a very large conventional “bunker-buster” weapon in the U.S. inventory — and on Iran’s deeply buried Fordow enrichment facility.

The MOP’s combination of mass, guidance and penetration capabilities has raised questions about whether it could meaningfully damage a hardened, underground enrichment complex such as Fordow, and what the regional, environmental and diplomatic consequences might be if it were used.

This article unpacks the technical facts, the operational constraints, the legal and diplomatic context, the humanitarian and environmental risks, and the realistic policy options available to the United States, Israel and other stakeholders. (Key sources include public technical descriptions of the MOP; facility histories and monitoring by the International Atomic Energy Agency (IAEA); and commentary from officials and analysts.)