The Crusades were a series of medieval wars initiated to reclaim Jerusalem for Christianity. Initially launched to protect eastern Christians, they evolved into a form of holy war promising heavenly rewards. The first crusade in the 11th century was prompted by political shifts in the Middle East, with the Seljuk Turks disrupting the balance of power.

Byzantine Emperor Alexios I sought help from the Pope to address this, leading to Pope Urban II's famous call for crusades in 1095. Despite capturing Jerusalem in 1099, subsequent crusades faced challenges, with the second crusade in 1147 proving a failure against Muslim forces led by Nuradin.

While achieving limited military success, the Crusades had a profound cultural impact on Europe and contributed to the decline of the Byzantine Empire.