By the middle of the 17th century, Spain had been drained by the vast strains of the Thirty Years' and related wars and began to slip into a slow decline. During the middle to late decades of the century, the Dutch, English and French were able to take advantage of Spain's shrinking, run-down and increasingly underequipped fleets. Military priorities in continental Europe meant that naval affairs were increasingly neglected. The Dutch took control of the smaller islands of the Caribbean, while England conquered Jamaica and France the western part of Santo Domingo. These territories became bases for raids on Spanish New World ports and shipping by pirates and privateers. The Spanish concentrated their efforts in keeping the most important islands, such as Cuba, Puerto Rico and the majority of Santo Domingo, while the system of treasure fleets, despite being greatly diminished, was rarely defeated in safely conveying its freight of silver and Asian luxuries across the Atlantic to Europe. Only two such convoys were ever lost to enemy action with their cargo, one to a Dutch fleet in 1628 and another to an English fleet in 1656. A third convoy was destroyed at anchor by another English attack in 1657, but it had already unloaded its treasure.