In the doctoral dissertation under the heading „Analysis of the work Obsidio Iadrensis – from text to author” a new thesis concerning the authorship of the work Obsidio Iadrensis, which according to the opinion of historians is considered to be one of the most valuable narrative sources for knowledge of Croatian 14th century history and one of the rare, but quality works of our Pre-Renaissance period, is carried out. By continuing and expanding previous research on the work that resulted in rejection of the formulated assumption about the authorship of Zadar archbishop Nikola Matafar, which brought the research back to the beggining, this doctoral dissertation starts with the determination of the literary genre of the Siege, after that follows the exploration of the particularities of content, language and style of the text that indicate the possibility that Obsidio Iadrensis is a compilation of texts, or rather excriptio and compillatio „of some very unclear paragraphs“ as the copyist of the Zagreb manuscript from the year 1532 himself warned us. The author's contradictory attitiude towards Zadar inhabitants and towards the description of the event in the letter to the purchaser is being investigated, as also the non-conformance of the content of the letter and the content of the work directs the investigation to the manner how the anonymous author forms the image of the Zadar inhabitants and how he explains the fall of the city in Venetian hands by God's interference in earthly matters, but also by concrete reasons that the citizens themselves take responsibility for. The discovered particularities and contradictions cannot only be justified by the possibilities of the text in the time of its emergence, because they testify to the different political convictions and the mental distance in the explanation of the events to which the work is dedicated to. The question of the authorship of the work Obsidio Iadrensis cannot be separated from the question of the origin of Zagreb manuscript and as the textual particularities that have been detected indicate the presence of different mentalities in the explanation of the described political events, as also the isolated analyzed linguistic and stylistic particularities, first of all the numerous, different names for God characterstic for the work, but also the way of time counting, than the author's contact with the reader and the explanation of supernatural events show the disconnectedness of the individual descriptions within the work and the possibiliy of their emergence in different periods of time. The untidy linear chronology, the different time counting, the different way of writing the same dates that follow one after the other, the abrupt transitions and the weak connection of the description, the fragmented descriptions in the work, and similar and repeated descriptions show that the work that has found its way to us does not match the author's statement in the letter to the purchaser that he was intending to create it in chronological order and to give a matter-of-fact description of the main cause of the conflict and the conflicts between the adversaries. The conclusion of the research of this doctoral dissertation is that Obsidio Iadrensis is not the complete work of one author, which additionally complicates the solution of the question regarding the authorship.