What fuelled the great explorations of Spain and Portugal weren't because they liked doing it, it was because silk and spices were super expensive to be traded along the Silk Road, past Arab states that imposed hefty taxes, and had to be shipped all the way across the Mediterranean Sea, where ports made fortunes by levying even more on the goods.
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The Grand Canal was key to China's reunification as it linked both its huge waterways to irrigate and drain China's agricultural zones. Thanks to this, which represented the longest waterway made by man, China's agricultural system prospered, and the population in agricultural areas has grown. Ships with provisions navigated through the canal, boosting the creation of huge urban areas next to its shores, which otherwise would have not been able to receive supplies with such ease.
It breached a long-standing line between domestic law enforcement and foreign military operations for the first time.
