When Israel and the United States struck Iran’s nuclear facilities last summer, the goal was clear: cripple Tehran’s ability to produce a nuclear weapon. The attacks damaged key enrichment sites and infrastructure.

But the fate of Iran’s most sensitive material—hundreds of kilograms of uranium enriched to 60% purity—remains uncertain, and much of it may still be buried deep inside hardened underground complexes.

All three enrichment plants known to have been operating before the conflict—two at Natanz and one at Fordow—were reportedly destroyed or severely damaged.