Fuggers lent against a prince's silver mines, not his word

Archduke Sigismund of Tyrol controlled some of Europe's richest silver deposits at Schwaz, but chronic overspending on his lifestyle and construction projects, plus war debts to Venice, left him perpetually short of cash despite sitting on a fortune in mineral wealth still in the ground. A conventional loan to a spendthrift ruler was a bad bet: princes routinely defaulted on debts, and a lender's only recourse against a sovereign who wouldn't pay was limited at best.

Augsburg banker Jakob Fugger structured his 1487 loan to Sigismund differently: rather than lend against Sigismund's promise to repay in cash, Fugger secured the debt directly against the archduke's silver mines, with the right to buy silver from Schwaz at a fixed, discounted price. The loan's security wasn't the archduke's word — it was physical bullion coming out of the ground regardless of how Sigismund managed his own finances.

Secured the loan against the silver mines, with the right to buy output at a discount, so repayment came from production regardless of the prince's finances.

The archduke's promise was worthless because he routinely defaulted and was a sovereign.

The silver mines produced value regardless of the archduke's finances.

Securing the loan against the mines meant default converted the debt into a claim on silver.

Each new loan deepened the Fuggers' claim, so the borrower's need for cash expanded their position.

When a borrower's promise is weak, secure the loan against a productive asset whose value doesn't depend on the borrower's discipline.

By the early 1500s the Fuggers controlled the whole of Schwaz's production and had acquired mines of their own in Tyrol and Carinthia, turning what began as one prince's debt into command of Europe's largest silver-mining region — Schwaz became the world's largest mining metropolis in the first half of the 16th century, and the family went on to apply the same asset-secured lending model to European nobility broadly, becoming the continent's preeminent banking dynasty.