The raids were such a problem coastal settlements were seldom undertaken until the 19th century. Between 1580 and 1680 corsairs were said to have captured about 850,000 people as slaves and from 1530 to 1780 as many as 1,250,000 people were enslaved. However, these numbers have been questioned by the historian David Earle. Some of these corsairs were European outcasts and converts (renegade) such as John Ward and Zymen Danseker. Hayreddin Barbarossa and Oruç Reis, Turkish Barbarossa Brothers, who took control of Algiers on behalf of the Ottomans in the early 16th century, were also notorious corsairs. The European pirates brought advanced sailing and shipbuilding techniques to the Barbary Coast around 1600, which enabled the corsairs to extend their activities into the Atlantic Ocean. The effects of the Barbary raids peaked in the early to mid-17th century.