In 1540, with revenue from Mexican mines, the Spanish settlers began the construction of Fort San Felipe del Morro ("the promontory") in San Juan. With the completion of the initial phase of the construction in 1589 El Morro became the island's main military fortification, guarded by professional soldiers. The rest of Puerto Rico, which had been reorganized in 1580 as a captaincy general, had to rely on only a handful of soldiers and the local volunteer militia to defend the island against militant and pirate attacks.