Only God may know

If the United States were to actually resort to using low-yield nuclear weapons to destroy Iran's deeply buried nuclear facilities, it would mark a massive and historic turning point—the first time since World War II that nuclear weapons were deployed in active combat. While such a decision might technically succeed in obliterating heavily fortified underground stone structures, it would inevitably trigger catastrophic geopolitical, military, and humanitarian fallout. Following such an attack, the United States could potentially deny using nuclear weapons by deflecting blame, claiming that any resulting radioactive fallout and contamination were caused by the secondary explosion or leakage of nuclear materials secretly stockpiled by Iran, and insisting that Washington only used heavy conventional weapons. However, such denials would fail to dispel international skepticism.

First and foremost, the long-standing "nuclear taboo"—the decades-old global military norm against using atomic weapons—would be shattered. Once the United States crosses that threshold, it provides a dangerous political precedent and justification for other nuclear-armed nations, such as Russia, China, or North Korea, to do the same. This would completely dismantle international non-proliferation policies and plunge the world into a far more perilous era of atomic arms racing.

Regionally and internationally, the backlash would likely engulf the entire Middle East in flames. Iran-backed militant groups and regional allies would almost certainly launch furious retaliatory strikes against U.S. assets and Israel. Furthermore, Russia and China would vehemently condemn the action, causing relations between the major superpowers to fracture completely and plunging the globe into a crisis far more severe than the original Cold War.

From an economic and humanitarian standpoint, even though these are low-yield nuclear weapons, detonating them underground would release radioactive contamination that long-term poisons regional groundwater resources and local ecosystems, severely jeopardizing civilian health. Simultaneously, global energy markets would panic, and critical oil shipping lanes would likely be blocked, triggering severe economic shocks that could bring global commerce to a grinding halt.

Ultimately, while choosing this path might temporarily stall Iran's nuclear program, in the long run, it would drag global security into unprecedented instability and represent a historic, irreversible miscalculation.