<diacritize> Two Dutch migrants to Munster Jan Mathys , a baker from Haarlem , and Jan Beuckelson , known as John of Leiden were to play a decisive role in developments there . <yor>Two Dutch migrants to Münster Jan Mathys , a baker from Haarlem , and Jan Beuckelson , known as John of Leiden were to play a decisive role in developments there . 