This article reconstructs the printing history of Hugo Grotius's Mare liberum (The Free Sea, 1609). It examines the political circumstances which prompted the pamphlet's publication, but then seemed to conspire against it, and relates these to Grotius's revision of chapter 12 of Ms. BPL 917 in Leiden University Library, the one surviving copy of De iure praedae (The Commentary on the Law of Prize and Booty, 1604-1608). While preparing chapter 12 for the press, he made a serious effort to tone down its bellicose rhetoric, erasing, for example, all references to the Spanish claims to the Americas. His aim was to placate the French envoy Pierre Jeannin and his own political patron Johan van Oldenbarnevelt, the driving forces behind the negotiations for the Twelve Years' Truce (1609-1621). In the context of these negotiations, Grotius was at pains to downplay his radical rights theories. The subjective right of punishment only received a mention in the conclusion of Mare liberum, for example. Yet a discarded outline for the pamphlet's preface shows that the argument of De iure praedae remained uppermost in his mind, witness the outline's denunciation of the 'poisonings, perfidy and crimes of the Portuguese'. Both De iure praedae and Mare liberum had been commissioned by the Dutch East India Company (VOC) for the express purpose of influencing political developments in its favour. Yet neither treatise had the impact originally intended by Grotius and the VOC directors. Ironically, these occasional writings became classics of international law instead.