The North African coast became the source of a particular set of sea raiders at the beginning of the seventeenth century. The Ottoman authority over the provinces of Tripoli, Tunis, and Algiers established the region as part of the Ottoman Empire by the 1560s, but this scarcely lasted to the end of the century in anything like an effective form. Instead local rulers emerged from the local military/ naval garrisons, with Ottoman pashas appointed to supervise, not always with much effect. These places had been bases for part of the Ottoman naval forces in the sixteenth century, but as the Ottoman imperial presence faded, naval activity in the region emerged as an official piracy. The raiders were called corsairs.

It took rather more than official neglect to drive the development of corsair activity. For one thing the Ottoman naval power was based on galleys, which were, as the Levant Company ships (and others) had by now demonstrated, vulnerable to well-armed sailing ships – and the biggest ships were the biggest prizes. But a new ingredient arrived at the beginning of the seventeenth century in the form of European pirates and privateers who had been infesting Atlantic and Mediterranean waters during the wars with Spain. These were from most of the lands north of Spain – France, the Netherlands, England, even Scotland and Scandinavia – and they were men who had found the privateering life congenial and satisfying, and were keen to continue in it. They had found that peace was not conducive to their activities, and as peace spread over Western Europe – the Franco-Spanish treaty ended one war in 1599, the Anglo-Spanish treaty brought peace in 1604, and the Dutch–Spanish armistice ended their fighting in 1609 – they had to find a new base, not being welcome any more to operate from their homelands. The one war which did not end was that between Spain and the Ottoman Empire. A combination of the slackening of Ottoman authority in North Africa, unemployed European pirates, and vulnerable merchant ships now led to the development of corsairs and corsair states.

The English had been trading with Morocco for half a century, and had even organised the Barbary Company to regulate the trade for a time.