Final answer:
The Crusades are characterized as 'successful failures' because, though they were largely military failures in terms of achieving lasting Christian control over the Holy Land, they inadvertently succeeded in other areas such as trade, expansion of kingdoms, and cultural exchange.
Step-by-step explanation:
The Crusades, starting from 1096 and ending in 1291, have been labeled as “successful failures” by historians. This reflects the complex nature of their outcomes. The First Crusade was somewhat successful in establishing Christian-ruled states in the Levant, making it the most triumphant militarily. However, subsequent crusades failed to maintain Christian control of the Holy Land, with the port city of Acre's fall in 1291 marking the end of the Crusader States. Beyond military endeavors, the crusades led to the persecution of Jews, and Muslim-Christian relations deteriorated significantly. Despite these failures, the crusades had unintended positive outcomes. They stimulated trade between East and West, facilitating the spread of new products and ideas, and contributed to the expansion and creation of new political entities in parts of Europe.