Law and War in Late Medieval Italy: the Jus Commune on War and its Application in Florence, c. 1150-1450 by Ryan Martin Greenwood A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Centre for Medieval Studies University of Toronto © Copyright by Ryan Martin Greenwood (2011) Law and War in Late Medieval Italy: the Jus Commune on War and its Application in Florence, c. 1150-1450 Ryan Martin Greenwood Doctor of Philosophy Centre for Medieval Studies University of Toronto 2011 Abstract This study, on law and war in late medieval Italy, has two primary aims. One is to review the legal tradition on war as it developed in the medieval jus commune, or common law, from approximately 1150-1300, and then to consider how that tradition evolved from roughly 1300-1450. In general the latter period still represents a lacuna in scholarship on the legal theory of war, and can be addressed as a distinct period because the fourteenth century was a time when theory moved in important new directions. It will be suggested in turn that those new directions were related to changing politics and institutions in Italy. The second aim continues and reflects the first, as it seeks to better understand how legal arguments about war and peace were employed in practice, using Florence as an example. The study finds that these legal arguments found their most important role in diplomacy. Florentine diplomatic records, as well as legal opinions (or consilia) on inter-city disputes, will help to examine the complex nature of that role. In general it will be seen that the law, ii including the jus commune, was a strategic tool and an important regulatory mechanism for relations between political actors in late medieval Italy, though one that also had significant limitations. The first chapter introduces the material and themes. The second treats the just war tradition and laws on war through 1300. The third chapter examines legal theory on war, particularly in Roman law, from roughly 1300 to the early fifteenth century. The fourth explores how just war arguments were deployed in Florentine political discourse between 1230 and 1430. The fifth chapter examines a range of legal issues related to war, as found in diplomatic instructions and consilia which played a role in Florentine wartime diplomacy from 1392-1402. The sixth chapter is the conclusion. iii Acknowledgments This study was made possible through the help of a number of individuals who I would like to acknowledge, and to whom I remain indebted. For this kind of endeavor, the resources at the Centre for Medieval Studies are hard to match. Among staff members, the assistance of the graduate administrator, Grace Desa, has been indispensable. Above all, the comraderie of fellow peregrini in this often strange medieval world made explorations of it worthwhile. I am indebted particularly to my friend Jon Robinson for conversations on medieval law and political theory, and to Jon again, and friends Jess Paehlke and Gur Zak, for an Italian reading group. The general direction of the thesis grew out of seminars on medieval law with Professor Lawrin Armstrong and on violence with Professor Mark Meyerson, and I wish to thank my supervisor, Lawrin Armstrong, for guidance and support, including work that I was able to do for him, and for this project, in Florence under the aegis of his SSHRC grant. Always relaxed in his approach, he offered copious good advice on various aspects of the project and Italian history, sometimes dispensed in long email missives or over a beer. At the Arthur W. Diamond Library of Columbia University Law School, the Special Collections Librarians Whitney Bagnall and her successor, Sabrina Sondhi, retrieved, and oversaw the retrieval of, countless dusty legal volumes. Their help in finding items, and their patience, made working there rewarding and pleasant. At the Law Library of Congress, Dr. Meredith Shedd-Driskell offered expert help, good advice and a great sense of humor to help the process along. Her wide interests, and her encouragement of the project over the course of a few summer visits, were welcome and greatly appreciated. In Florence, iv the large staff at the Archivio di Stato was always helpful, as was the staff at the Biblioteca Nazionale. While there, Dr. Luca Boschetto shared his deep knowledge of the archives and equally deep insights on Florentine humanism and law. In the final stages of writing, Filomena Calabrese checked over Italian transcriptions, and Danielle Winter helpfully gathered bibliographic references. All faults that remain, in form and content, are mine. Finally the support of my family was essential, and I thank my parents, above all, for their steady encouragement, particularly in view of the time and effort it took to complete the dissertation. They stood behind a long education and the project: this is for them. v Table of Contents Abstract ........................................................................................................................................... ii Acknowledgments .......................................................................................................................... iv Contents .......................................................................................................................................... vi Abbreviations ................................................................................................................................ vii 1. Introduction ................................................................................................................................. 1 2. Laws of war and the just war tradition to 1300 ........................................................................ 21 3. War and peace in the fourteenth-century jus commune ............................................................ 66 4. The just war in Florentine political discourse ......................................................................... 119 5. Diplomacy and law in Florence‟s war with Milan, 1392-1402 .............................................. 155 6. Conclusion .............................................................................................................................. 220 Bibliography ................................................................................................................................ 240 vi Abbreviations Cap Capitoli C. Codex Justinianus. In Corpus Juris Civilis. Ed. T. Mommsen, et al. Vol. 2. Berlin: Weidmann, 1892-95. Repr. 1954. C. Causa in Pars Secunda of the Decretum Gratiani. In Corpus Juris Canonici. Ed. A. Friedberg. Vol. 1. Leipzig: B. Tauchnitz, 1879. Repr. Graz: Akademische Druck-u. Verlagsanstalt, 1959. D. Digesta Justiniani. In Corpus Juris Civilis. Ed. T. Mommsen, et al. Vol. 1. Berlin: Weidmann, 1892-95. Repr. 1954. HFP Leonardo Bruni. History of the Florentine People. Vol. 3. Ed. and trans. James Hankins. Cambridge, Mass.: Harvard University Press, 2007. DBLC Dieci di Balìa, Carteggi, Missive, Legazioni e Commissarie Minerbetti Cronica volgare di anonimo fiorentino dall‟anno 1385 al 1409, già attribuita a Piero di Giovanni Minerbetti. Ed. Elina Bellondi. In Rerum Italicarum Scriptores, xxvii, pt. 2. Città di Castello: Lapi, 1915 and Bologna: Zanichelli, 1917-18; repr. Turin: Bottega d‟Erasmo, 1966-69. Morelli Giovanni Morelli. Ricordi. In Mercanti scrittori. Ed. V. Branca, 101-339. Milan: Rusconi, 1986. SCMLC Signori, Carteggi, Missive, Legazioni e Commissarie SCMC Signori, Carteggi, Missive, I Cancelleria Sext. Liber Sextus Decretalium Bonifacii VIII. In Corpus Juris Canonici. Ed. A. Friedberg. Vol. 2. Leipzig: B. Tauchnitz, 1879. Repr. Graz: Akademische Druck- u. Verlagsanstalt, 1959. X. Decretales Gregorii IX. In Corpus Juris Canonici. Ed. A. Friedberg. Vol. 2. Leipzig: B. Tauchnitz, 1879. Repr. Graz: Akademische Druck-u. Verlagsanstalt, 1959. vii Chapter 1 Introduction This study examines the development of the theory of war in the jus commune, or common law, of the late Middle Ages, and considers how such legal theory was put into practice by the government of Florence in the same period. In particular, the study examines the law on war in the fourteenth century in detail, and places Florentine wartime diplomacy in the context of its legal disputes and negotiations, in the period 1388-1402. This latter investigation takes its lead from the outstanding work of Lauro Martines on the involvement of lawyers in Renaissance Florentine government and diplomacy, Lawyers and Statecraft in Renaissance Florence (1968).1 Unsurpassed in forty years, Martines‟s book brilliantly explores the roles that lawyers played in shaping domestic law and policy in Florence and in negotiating foreign treaties and disputes. This thesis takes a somewhat different course, considering the development of the law itself and its role in Florentine foreign relations. To this end, it brings commentaries on the jus commune into sharper focus, and examines a series of legal opinions (consilia) on disputes that arose during Florence‟s conflict with Giangaleazzo Visconti of Milan. The aim is to shed some new light on what were processual and highly deliberative relations between the Italian cities in the period. The first half of the study concerns the legal theory of war in the jus commune – which comprised medieval canon, Roman and feudal law – and is intended to provide a foundation for the second half. It is also hoped that the first half can stand as an 1 Lauro Martines, Lawyers and