In 1620 Jan Janszoon met a Dutch men-of-war in the area of Malaga. When the ship noticed the corsairs it immediately altered its course and sailed directly after them while raising the red flag (this means that no quarter will be given). After seeing this Janszoon turned and fled from the advancing ship. According to the Dutch consul in Algiers the ship was not a men-of-war, but a courageous merchant that bluffed his way out of the meeting. Not long after this, in June and July of 1620, Janszoon was again capturing ships. Contrary to De Veenboer he did not distinguish between Dutch and other ships though.
While in Algiers Janszoon was converted to the Islam and took a second wife which is acceptable according to the Islamic faith. He also adopted the name of Murat Reis (Murat, Morat, Murate or Morato). In 1623 Janszoon took Salé (in Morocco) as his base of operations. Algiers was no longer a suitable harbour at that time to sell the cargo and or the captured ships, because Algeria had made peace with several European nations. Janszoon soon built a fleet of 16 to 17 ships. The vessels were fast and well provisioned. He managed to make Salé almost as feared as Duinkerken (in Belgium).
Salé became very prosperous and consequently declared itself independent from Morocco. After an unsuccesful siege by Morocco the Sultan eventually acknowledged it's suzerainty. The main sources of income of Salé were piracy, shipping and dealing in stolen property. Janszoon went privateering in the North sea, the North-Atlantic sea and the Canal. In November 1623 he went to the Dutch Harbour Veere, because he needed to make repairs. The authorities could not deny the two ships access to Veere because at that time several peace treaties and trade agreements existed between the emperor of Morocco and the Dutch Republic. Several dutchmen joined his crew when he left in December despite their being prohibited to do so by the Dutch authorities. His first, Dutch, wife visited Janszoon while he was there. During the repairs some of their Spanish prisoners escaped. Out of compassion they were hidden by sympathizers. The pirates did not get any help with locating the escaped prisoners so the first thing they did after sailing out of the harbour of Veere was attack several French ships despite the treaties and agreements.
Several years later, in the month of February 1626, Janszoon was again in Holland, though under different circumstances. He had left Salé with 3 ships and had apparantly captured a rich Spanish prize which he hoped to sell in the Dutch Republic. When his ships arrived in the North sea they spotted what appeared to be a rich Dutch merchant ship with only a few men on guard. They went along-side, but just when fifty of their crew had boarded the ship the Dutch flag was struck and the Spanish flag went up instead. They were immediately attacked by the crew that had hidden itself. The ship turned out to be a Spanish privateer from Duinkerken. One ship was almost immediately disabled and forced to surrender. The other two ships barely managed to get away heavily damaged and with many dead and casualties. One of the ships managed to sail into the Maas river. The most heavily damaged one was able to reach the IJ of Amsterdam, via the Isle of Texel, where they had a hard time getting medical aid. The ship in Amsterdam was sold and the pirates left with the ship that had entered the Maas early in 1627.
After this voyage Janszoon was mainly active in Salé as a dealer in stolen goods. His reputation seems to have suffered from this less adventurous profession. Early in 1627 he went further north than he had previously sailed: Iceland. In the harbour of the capital he attacked a ship and imprisoned several of it's crew. On the way back he also took a Dutch vessel and imprisoned more people. The people were sold as slaves in Salé. In 1631 we hear from him again. In this year he sailed for England and Ireland. He landed there with his men and managed to imprison about two hundred men who were sold as slaves in Algiers.
From 1631 to 1640 not much is known about his actions. Janszoon had to leave Salé because of political reasons and seems to have lived in Algiers and Tripoli for some time. He may have been captured by Malthese Knights for a short period, but whether this is true remains unclear. In 1640 he was employed by the Emperor of Morocco as the Governor of the Castle Maladia on the West coast of Morocco. In 1640 his Dutch daughter, Lysbeth Janszoon, sailed to Morocco to visit him. The last thing that is known is that he and his daughter were still at the Castle of Maladia in August 1641.