The Silkworm Farm

A province's wealth came from silk. The silk came from silkworms. The silkworms ate only mulberry leaves.

A blight struck the mulberry trees.

Within a year: no leaves, no silkworms, no silk, no trade, no taxes, no soldiers' pay.

The governor asked his advisors how a tree disease had emptied his treasury.

They showed him the chain. He hadn't known it existed.