• The U.S. has approximately 30 days of heavy rare earth supply (terbium and dysprosium) for defense needs, requiring 500 tons of dysprosium and 150 tons of terbium to ensure military continuity during disruptions.
• Terbium and dysprosium are critical for NdFeB magnets in defense systems including fighter aircraft, missiles, submarines, and radar—without them, modern military platforms cannot function.
• China dominates heavy rare earth refining and magnet production, creating strategic vulnerability for Western defense supply chains where the real bottleneck is separation, metallization, and manufacturing capacity, not mining alone.

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Rare earth supply chains rarely make front-page news. But this week’s geopolitical environment—and the fragile state of heavy rare earth inventories—should remind investors that some of the most strategically important materials in modern warfare are measured not in years of supply, but in weeks.

A quantitative analysis covered previously in Rare Earth Exchanges™ found that the United States’ effective strategic coverage of heavy rare earths—especially terbium (Tb) and dysprosium (Dy)—may amount to roughly 30 days of defense-related supply under disruption scenarios.  Now this study has its limitations and the national defense stockpiles could be more, but the message is clear.

The study argued that maintaining military continuity would require stockpiling about 500 metric tons of dysprosium and 150 metric tons of terbium, a gap that highlights the fragility of Western supply chains for these critical elements. That vulnerability matters even more in the current geopolitical environment. Terbium and dysprosium are essential additives in neodymium-iron-boron (NdFeB) magnets, where they provide high-temperature stability for motors and guidance systems used in fighter aircraft, submarines, missiles, and radar systems.

In practical terms, these obscure metals sit inside the electric motors that control missile fins, radar positioning systems, and precision weapons. Without them, modern defense platforms cannot function.

The Supply Chain Reality

Heavy rare earth elements remain among the most concentrated resources in the global critical minerals economy. China dominates refining capacity, while supply from regions like Myanmar has historically flowed directly into Chinese processing systems. Even small disruptions can ripple through defense manufacturing and advanced industrial sectors.

Financial analysts and policymakers increasingly warn that heavy rare earth supply is one of the most vulnerable nodes in the Western industrial base. China controls the overwhelming share of refining and magnet manufacturing capacity, giving Beijing significant geopolitical leverage during trade disputes or international conflicts.

This reality has not gone unnoticed in Washington. The U.S. Department of War has begun funding projects aimed at expanding the domestic supply of terbium and other rare earths, including recycling initiatives designed to recover magnet metals from waste materials.

Strategic Implications

The convergence of three forces—geopolitical tension, fragile heavy rare earth inventories, and rising defense demand—creates a stark strategic question:

How resilient is the Western rare earth supply chain if disruptions occur tomorrow?

Rare Earth Exchanges has repeatedly argued that the real bottleneck is not rare earth mining alone but heavy rare earth separation, metallization, and magnet production. Until those midstream and downstream capabilities expand outside China, the West remains exposed to supply shocks.

In short, rare earths are no longer just industrial commodities.

They are strategic materials—and in the case of terbium and dysprosium, the clock on supply security may be measured in days, not decades.