Editing History of Christianity (section)

===Schism, crusade, spread, and retraction===
The Church of the East, which had separated after Chalcedon, survived against the odds with help from Byzantium.{{sfn|Angold|2006|loc=frontmatter}} At the height of its expansion in the thirteenth century, the Church of the East stretched from Syria to eastern China and from Siberia to southern India and southern Asia.{{sfn|Koschorke|2025|p=XXIII}} The second separation between east and west took place in 1054 when the church within the Byzantine Empire formed Byzantine [[Eastern Orthodoxy]], which thereafter remained in communion with the [[Ecumenical Patriarchate of Constantinople]], not the Pope.{{sfn|Ware|1993|pp=11, 33}} 
 
Along with geographical separation, there had long been many cultural differences, geopolitical disagreements, and a lack of respect between east and west.{{sfn|Kolbaba|2008|pp=214; 223}}{{sfn|Meyendorff|1979|loc=intro}} Nevertheless, the Byzantine emperor [[Alexios I Komnenos]] still asked [[Pope Urban II]] for help with the [[Seljuk Empire|Seljuk Turks]] in 1081,{{sfn|Rosenwein|2014|pp=173–174}} and Urban asked European Christians to "go to the aid of their brethren in the Holy Land" in 1095.{{sfn|Folda|1995|pp=36; 141}}{{sfn|Tyerman|1992|pp=15–16}}{{sfn|Bull|2009|pp=346–347}} 

Urban's message had great popular appeal. Drawing on powerful and prevalent aspects of folk religion, the [[First Crusade]] connected [[pilgrimage]], [[Charity (practice)|charity]], and [[absolution]] with a willingness to fight.{{sfn|Bull|2009|pp=346–349}}{{sfn|Van Engen|1986|p=523}} It gave ordinary Christians a tangible means of expressing brotherhood with the East and carried a sense of historical responsibility.{{sfn|Bull|2009|pp=340–342; 346; 349–350; 352}} The [[Crusades]] contributed to the development of national identities in European nations and, eventually, increased division with the East.{{sfn|Kostick|2010|pp=2–6}} The evolving [[Chivalry|cult of chivalry]] of the Christian knight became a powerful social and cultural influence before its decline during the 1400s.{{sfn|Bull|2009|pp=346-348}}{{sfn|Matthews|Platt|1998|p=208}} One significant effect of the Crusades was the invention of the [[indulgence]].{{sfn|Bull|2009|p=351}}

Christianity was declining in Mesopotamia and inner Iran, although some Christian communities continued to exist further to the east.{{sfn|Micheau|2006|pp=373, 378, 381}}{{sfn|Hamilton|2003|p=xi}} As churches in Egypt, Syria, and Iraq became subject to fervently Islamic militaristic regimes, Christians were designated as [[Dhimmi|''dhimmi'']], a status that guaranteed their protection but enforced their legal inferiority.{{sfn|Micheau|2006|pp=373, 403}} Different communities adopted various survival strategies: some withdrew from interaction, others converted to Islam, and others sought outside help.{{sfn|Micheau|2006|p=403}} 

The [[Christianization of Scandinavia]] occurred in two stages: first, in the ninth century, missionaries operated without secular support; then, a secular ruler would begin to oversee Christianization in their territory until an organized ecclesiastical network was established.{{sfn|Sanmark|2004|pp=14-15}} By 1350, Scandinavia was an integral part of Western Christendom.{{sfn|Brink|2004|p=xvi}}