Well it depends what they are in need of. They most commonly would want more land for their country to build and farm on. They may want land with fertile soil for farming. They may want the land because of it's geography, for example, for simple trade routes leading to and from the areas around north America (Canada, Mexico) etc.
The year 622 brought a new challenge to Christianity. Near Mecca, Saudi Arabia, a prophet named Muhammad claimed he received a revelation that became a cornerstone of the Islamic faith. The Koran, which Muhammad wrote in Arabic, identified Jesus Christ not as God but as a prophet. Islam spread throughout the Middle East and into Europe until 732.Soon thereafter, European Christians began the Crusades, a campaign of violence against Muslims to dominate the Holy Lands—an area that extended from modern-day Turkey in the north along the Mediterranean coast to the Sinai Peninsula—under Islamic control, partially in response to sustained Muslim control in Europe. The city of Jerusalem is a holy site for Jews, Christians, and Muslims; evidence exists that the three religions lived there in harmony for centuries. But in 1095, European Christians decided not only to reclaim the holy city from Muslim rulers but also to conquer the entire surrounding area.
