When the works written by eyewitnesses of the First Crusade at the end of the 11th century are found insufficient for illuminating certain events, the records of contemporary authors from that time come to the fore. In this context, the Historia Hierosolymitanae expeditionis takes first place, written by Albericus Aquensis (i.e., Albert of Aachen in English) as a contemporary author of the time. His Historia is a most detailed and colorful depiction of the expedition and a unique work about the Islamic-Crusader struggle between 1096-1120 in Anatolia and the Near East. This article will evaluate the Historia by examining it in terms of its value as a resource.

Although not much information is known about the author’s life, he is understood from the records in his work to have originated from Aachen (Aix la Chapelle) in the Rhineland. The author is also understood to have probably been born before 1080 at the latest and to have served as a canon (priest) at the Church of Saint Mary in Aachen and, thanks to his monastic education, gained the skills to write his work in Latin. Although Albert was a clergyman, he used a secular language.

Albert never came to the East in person, but managed to create his work to serve as a lesson for the next generations based on the testimonies from eyewitnesses who had participated in the expedition as well as what he heard from others. In the 19th century, some historians became selective in their own way and considered some of the information they found reasonable to be based on a lost source, while other parts were simply fables. However, all these claims had yet to pass beyond being theories until now. Albert used the oral statements from the Crusaders who’d returned from the expedition as a source and did not benefit from any known written works that have survived to the present day.

However, debates have occurred since the middle of the 19th century about how historically reliable Albert's work is. Although the work had been seen as an indispensable source despite its internal inconsistencies, especially in terms of geographical knowledge and chronology, historians still approached the information in the Historia with caution. The author’s contradictory repetition of events from time to time, or his early chronological description of an event that actually had taken place at a later date, as well as his mistakes regarding topography led to criticisms and doubts. However, the information he conveyed was determined to be largely consistent with the Eastern Christian and Islamic sources and to in general correctly reflect the course of events. Without Albert's records, a serious lack of data would be found when evaluating the process of how the Latins had settled in Northern Syria and the Middle East. No other source exists that gives a more detailed or more informative view about how the County of Edessa was established in 1098. Albert's work is also invaluable with its detailed statements in terms of dealing with the First Crusades of 1101, which is extremely important for Turkish Anatolian history.

The Historia, of which 13 manuscripts and 12 books have survived, concerns the years 1095-1120. The author narrated the First Crusade from the perspective of Lorraine and dealt with events mostly from the perspective of Godefroi de Bouillon and the County of Edessa, mainly focusing on the history of the Kingdom of Jerusalem. The only contemporary Latin source with which these records in the Historia containing important details about the early period of Latin states in the East can be compared is the work by Fulcher of Chartres and his Gesta Francorum Iherusalem Peregrinantium [A History of the Expedition to Jerusalem], in which he narrates the developments that had taken place up to 1127. Albert importantly emphasized that he had obtained information from reliable sources while copying his work, as this shows that he had confirmed the information and had not depended upon a single source. Albert not only narrated the historical process and military events, but also included various details that seemed interesting to him in his work and tried to explain the experiences and observations experienced during this time through as many aspects as had been conveyed to him.

As a result, Albert's Historia offers the broadest description of the First Crusade and fills in the gaps regarding other cases where eyewitness authors had left some events obscured. Although one cannot expect absolute impartiality from Albert, many of the statements the author mentioned have also been confirmed by Eastern sources. However, the work should be studied carefully, as sometimes it provides inaccurate information in terms of geographical information and chronology. The author sometimes repeated events and other times ignored the chronological order or included some legendary tales. Regardless, the Historia is a unique work about the First Crusade and the establishment of Latin states in the East, especially with regard to the period of the First Crusader ruler of Jerusalem, Godefroi de Bouillon (1099-1100), and his successor, King Baldwin I of Jerusalem (1100-1118). Historia contains many unique and important details not found in any other source.