|Richard I of England|
The Crusades were predominantly a series of religious wars undertaken by the Latin Church between the 11th and 15th centuries; historians cannot agree on any single definition of a crusade, or which specific military campaigns should be included. Crusades were fought for many reasons: to capture Jerusalem, recapture Christian territory or defend Christians in non-Christian lands, resolve conflict among rival Roman Catholic groups, gain political or territorial advantage, or to combat paganism and heresy.
The First Crusade arose after a call to arms in a 1095 sermon by Pope Urban II. Urban urged military support for the Byzantine Empire and its Emperor, Alexios I, who needed reinforcements for his conflict with westward migrating Turks in Anatolia. Although one of Urban’s stated aims was to guarantee pilgrims access to the holy sites in the Holy Land that were under Muslim control, scholars disagree whether this was the primary motivation for Urban or for the majority of those who heeded his call. Urban’s wider strategy may have been to unite the Eastern and Western branches of Christendom, which had been divided since their split in the East–West Schism of 1054, and establish himself as head of the unified Church. Similarly, some of the hundreds of thousands of people who became crusaders by taking a public vow and receiving plenary indulgences from the church were peasants hoping for Apotheosis at Jerusalem, or forgiveness from God for all their sins. Others, historians argue, participated to satisfy feudal obligations, gain glory and honour, or find opportunities for economic and political gain. Regardless of the motivation, the response to Urban’s preaching by people of many different classes across Western Europe established the precedent for later crusades.
Actions carried out at least nominally under Papal authority during the crusades have polarised historians. Contrary to their stated aims and promises, crusaders often pillaged as they travelled, and their leaders retained much of the captured territory rather than returning it to the Byzantines. The People’s Crusade included the Rhineland massacres: the murder of thousands of Jews. Constantinople was sacked during the Fourth Crusade, rendering the reunification of Christendom impossible. These and other controversial actions were incongruous with the stated aims and implied moral authority of the papacy and the crusades, in one case to the extent that the Pope excommunicated crusaders.
The crusades had a profound impact on Western civilisation: they reopened the Mediterranean to commerce and travel (enabling Genoa and Venice to flourish); consolidated the collective identity of the Latin Church under papal leadership; and were a wellspring for accounts of heroism, chivalry and piety. These tales consequently galvanised medieval romance, philosophy and literature. The crusades also reinforced the connection between Western Christendom, feudalism, and militarism.
Editor’s note While not having researched the matter in great depth, about ten minutes, I find the video above far more instructive as to the reasons for the Crusades than any of the histories I found.