This project will address the problem of the compartmentalized academic study of the diverse Frankish- and Islamic-ruled societies through the first comprehensive study of Christianities in the Middle East. It aims to study the inter-Christian and Christian-Muslim interactions, on the assumption that these interactions contribute to shaping these communities. Although each Church has been partly studied for its own sake, no analysis of the cross-flows between the churches and with the sovereign powers that have ruled the Middle East from the 12th to the 16th c. has yet been carried out. It is time for a comprehensive and connected history of Christianities in the Middle East. Decompartmentalizing historiographies implies reading new archival sources along with known published texts from a connected history perspective and moving the analysis of communities from their centers to areas of contact. Jerusalem, owing to its centrality in terms of archives and practices, will be placed at the heart of the project, in tension with the regional space as a whole. ChrIs-cross has three main objectives: • To integrate the history of Christianities within the Islamicate world by identifying the actors, places and different contexts of exchange, from a bottom-up perspective; • To study the Christian communities of the Middle East at a pivotal moment, that of reconfiguration in confrontation with the progress of Islamization, through the strategies of Christian churches and communities, and the role of local authorities, both Christian and Muslim; • To provide both a global and a local vision of Jerusalem through a survey of the impact of intercommunity relations on the urban transformation, supported by a geographic information system: as a global city, Jerusalem is likely the manifestation of a plurality of interactions between the Christian and Islamic worlds, that provides a key to understanding the growing integration of the Middle Eastern region.