The Calvinist minister Godfried Udemans (1581/2–1649) is generally considered to be one of the more important seventeenth-century theologians from the province of Zeeland. He specialized in writings for a broader public, including, in particular, publications on ethical and religious codes in trade and seafaring. Of his various writings on moral theology, 't Geestelyck roer van 't coopmans schip, first published in 1638, is the most important.The Spiritual helm appeared in print some thirty years after Grotius occupied himself with De jure praedae (the manuscript dates from 1604), but Udemans had already begun articulating his thoughts in 1608. It is instructive to examine the ethical writings of a contemporary of Grotius. It has been claimed that in the early modern period, Calvinism, especially in its English Puritan variety, did much to propagate the medieval traditions of holy war that to all appearances had been laid to rest by Spanish theoreticians during the sixteenth-century Renaissance. In this article, I examine the extent to which Udemans draws upon religion as a means of legitimizing violence on behalf of secular political authorities such as the prince (or, as in the case of the Dutch Republic, the States or States General), and, more in particular, the Dutch East India Company (VOC) and West India Company (WIC). If Udemans is representative of the religious tradition to which he reckoned himself, holy war thought did not figure prominently in Dutch Calvinism.