Long ago back in 1095 Pope Urban the ll called for military support to help the Byzantine Empire for they lost holy land to the Muslims and needed support causing the first crusade.
Reasons of the Past
Finally once the support arrived the Christians took their holy land back and celebrated the victory! The Christians had the land for many years until the Muslims decided to fight back.
The End of the Crusades
We should trade swords for crops!
After many years of having obtained the holy land, it was taken by a great Egyptian general by the name of Saladin. Saladin was an outstanding general and by taking the holy land the Christians wanted it back launching the third crusade. Without the full support that wasn't given to the Christians, Saladin captured and killed much of crusader forces.
Long live the Ottoman Empire!
Before the crusades had even started a man by the name Charles Martel established that the religion of Europe would be Christianity by defeating the Muslims in a great battle. This gave the Muslims the point of view that taking the holy land for themselves would be the best.
I declare Europe under Christian religion!
When the crusades where no more it seemed as though it was a true failure but even though the Christians never got the holy land back, they did however make the catholic church more power, caused trade to occur with the Arabs and they even made better maps to explore more of Europe.
Ultimatley Christianity did not hold a long term religion in most of Europe like the crusades had hoped for. Instead the great Ottoman Empire arose and became the great empire in history lead by Suleiman the Magnificent leaving Europe mostly Muslim faith as how it remains today.