Just five years after the edition of the calendars of papal letters and documents for Pope Lucius III, Ulrich Schmidt and Katrin Baaken published the calendars for 1185-1187, covering the pontificates of his successors Urban III and Gregory III. The majestic volume strikingly illustrates the wide-flung, incessant activity of both of these popes. In the opinion of historians they are usually overshadowed by their predecessor Alexander III and their eventual successor, the great Innocent III. However, the 1545 calendar entries (c.1300 alone for Urban III) vividly recall the significance of the years 1185-1187, when imperial and papal politics were especially closely intertwined. After the marriage of Henry VI to Constance of Sicily in 1186 and Henry's coronation at Milan by the patriarch of Aquileia, Urban--more or less isolated at Verona during his entire pontificate--became an inveterate opponent of the Empire, refusing to grant Henry the imperial crown and was on the verge of excommunicating Henry's father, Emperor Frederick I Barbarossa, when he died in 1187. During his extremely brief pontificate (10/21/1187-12/17/1187) Gregory VIII, confronted with the loss of Jerusalem, had to attempt to reach an accommodation with Frederick in preparation for a new crusade. Thus the papal calendars for these two eventful years are most appropriately included among the Regesta Imperii, as Professor Klaus Herbers points out in his brief introductory note (p. v). This does not mean, of course, that the pontificates of Urban III and Gregory VIII are less significant at the ecclesiastical level. Both popes had long, distinguished careers as members of the cardinalate and the ecclesiastical hierarchy before they were elected to the papacy, and were experts in canon law. Appeals and the systematic use of papal judge delegates had vastly increased the demands on the efficiency of the papal curia in this period, while at the same time demonstrating the centrality and the primacy of the Roman papacy that were strongly reinforced by both popes. The curia issued more than 1500 documents over these two years, increasing production by more than a third compared to the numbers provided for their predecessor, Lucius III. Statistics for Lucius' reign indicate 1.54 documents per day, whereas the figures for Urban and Gregory VIII combined show 2.06 items per day (p. viii).
The calendars are organized in the manner usual for the Regesta Imperii and in particular the volume for Pope Lucius III.  The bases are extant papal letters and documents, either originals or copies, and letters that are known to have been issued by the papacy on the basis of their mention or quotation in other sources. If a document is undated or the dating criteria are uncertain, the editors decided to list the item at the last possible chronological point. At times it was impossible to determine whether a letter was issued by either Urban III or Gregory VIII or even later popes. In these instances the editors inserted the complete pertinent calendar entry under Urban III with a cross reference to that text under Gregory VIII. 320 documents exist in the original (21%), 653 documents survived as copies or as inserts in historiographical works (42%). Some 50 items were (also) transmitted in the canonistic literature. Known deperdita amount to 450 documents (29%) associated with the two pontificates of the years 1185-1187. Users will note with deep gratitude that the editors have also included a few cases among the calendars that strictly speaking do not represent a letter or document, such as some of the materials regarding the quarrel between emperor and pope over Archdeacon Folmar, the imperial candidate for the archbishopric of Trier (#154, #155, #159, #172, #173, #542, #652, #976, #977, #1277, #1293, #1298, #1399 and three forgeries: #+170, #+1278 and #+1538). Other examples of this type include election and death notices for the pontiffs (#1, #1296, #1297, #1545 ).
Each calendar of the letter or document gives underneath the date of the item (whenever possible also indicating the address used) a brief summary of the content, followed by the first five words of the incipit and subsequently the dating clause. The following paragraph is devoted to the pertinent transmission, listing manuscripts and printed editions by date and location, concluding with a reference to Jaffé-Loewenfeld's Regesta pontificum Romanorum whenever applicable. The calendar entry concludes with an exhaustive and critically analyzed bibliography that is an outstanding witness to the efforts of the editors. In the case of solemn privileges with the signatures of pope and cardinals, printed in full, the signatures appropriately precede the dating clause.
The massive volume is made supremely useful to historians of the twelfth-century papacy and the Hohenstaufen dynasty by its excellent indices and tables. Again all five initial words are cited in the index of incipits (pp. 761-768). The annotated signatures of the cardinals are listed separately for the pontificates of Urban III and Gregory VIII (pp. 769-781). Concordances for the various divisions of the P. F. Kehr Papsturkunden project (pp. 783-789) and concordances for Jaffé-Loewenfeld (789-794) precede the list of all of the calendars that cannot be definitely attributed to a particular pontiff, going back to Alexander III and extending to Gregory IX (pp. 795-800). Additions and corrections to the calendars of Pope Lucius III, including 12 entirely new items, are found on pp. 801-821, and the extensive bibliography on pp. 823-890. The impressive, beautifully produced work concludes with an index of names of persons and places (pp 891-976).
1. J.F. Böhmer, Regesta Imperii IV. Lothar III. und ältere Stauf 1125-1197, 4. Abteilung: Papstregesten 1124-1198, Teil 4, Lieferung 2: 1184-1185, ed. Katrin Baaken and Ulrich Schmidt (Böhlau Verlag: Cologna/Weimar/Vienna, 2006).