You do know the crusades were an answer by the Byzantine government In response to Arab Muslim pirates off of North Africa and in the Mediterranean. The Islamic fundamentalist pirates used terrorism by sinking Roman and later Byzantine vessels without even looting them. They killed and beheaded the crews and sunk the boats full just to "strike a blow to the main artery of the beast" - that Muhamed guy...
Sooooo the crusades were for sure terror filled and insane but I wouldn't exactly call it terrorism per se.. It was more of an answer too terrorism by saying "whelp you've been poking us for 400 years... Time for payback"
The Byzantium rulers approached the Vatican and said "hey bro... These brown people be fucking up our banks and shit so we can't pay you guys good tithings... Sorry bro but unless you help us fight the Muslims... I can't pay no mo"
So the Vatican being the G's they are put on the dresses and the big hats and called up there Viking buddies and we're all like "so yo... You Varangians wanna go smash something?" And being of Viking decent they said "fuck ya bro lets roll!" And the rivers ran red with Arab blood....
Soooooo moral of the story.... Don't fuck with anyone who's got Vikings for security guards...
This isn't even close to true. You can also scroll all the way down for a TL;DR.
The Varangians are also known as the Varyags who founded the medieval state of Rus which would turn into Russia. The made their way down the Danube and Volga from the Baltic Sea and ended up in the Black Sea, where in the 800s - as I mentioned - they'd settle Novgorod and then later Kiev. They then would actually attack Constantinople and sail down the Dnieper into the Black Sea and raid around the Byzantine Empire. After the state of Kiev Rus was Christianized one of the Varyag Kings sent a large amount of men to the Byzantine Emperor to help him out, because the Byzantine Emperor didn't trust the Byzantine Guardsmen who would turn on the Emperor if paid enough.
The First Crusade had a myriad of reasons that it happened and it was very complex. Mostly what a lot of Historians point to is that when the Saxons, Hungarians, and Vikings were Christianized it was suppose to bring stability to Europe, but after the collapse of the Carolingian Empire, you had an entire class that was based around warfare (the nobility) who had little to do but fuck each other up. Another factor is that the Eastern Orthodox and Catholic Churches have been in a schism since 1054, and Pope Urban II might have wanted to impose Catholicism on Byzantium.
The Byzantine Empire was also in decline having lost North Africa, Syria, Egypt, and was losing the fight against the Seljuq Turks and other Turkish tribes in Anatolia. After one of the most famous battles in history, the Battle of Manzikert, the Byzantines lost all power in Anatolia to the Seljuq Turks and the Empire nearly collapsed. After Manzikert the Pope called for soldiers of Christ to assist the Byzantines, but he was largely opposed by the Europeans. Then in the Middle East you had the Shi'ite Fatimid Caliphate which was also in conflict with the Seljuq Turks and other Turkish tribes, and the resulting warfare and Jerusalem falling to the Turks, then being recaptured by the Fatimids made pilgrimages a very dangerous thing for Christians from Europe.
What triggered the First Crusade was also another incredibly famous event, the Council of Clermont. Alexius Komnenos the Byzantine Emperor sent envoys to Europe requesting military aid because the Seljuqs had pushed all the way to Nicaea, which is close to Constantinople, and also the site of Christianity's first ecumenical council (hence the prayer the Nicene Creed). The envoys were received by Pope Urban II who - as aforementioned - might have wanted to do this to bring the Eastern Orthodox Church under Papal Primacy by giving military aid, thus mending the schism. He traveled to France, and went all over calling for peace among Christians to go fight the infidel Muslims, and famously called for three things: orthodoxy, reform, and complete submission to the Catholic Church. The Council of Clermont imposed a lot of things on the European nobility, such as they could only fight on Monday, Tuesday, Wednesday, and King Philip's excommunication was elongated. This was also where the famous Crusading phrase "Deus vult" (God Wills It) came from. He asked for Christians, rich and poor, to fight the Muslims and retake the Holy Land literally because "Deus vult." He then went a step further and said that any Christian who fought in the Crusades and killed in the name of Christ would be granted a remission of sins (thus we also have the first indulgences).
You then have a bunch of minor nobles, and second sons of Kings and other major nobles who get told: You've been sinning, and we the Church know this. You've been adulterous and murderous,
but if you go East, help the Byzantines, kill Muslims and Jews, retake the Holy Land in the name of Christ all that will be forgotten
and you'll get to keep land and everything you loot. To them, this was a miracle because they were already fighting, raping, and pillaging each other for things so sample as: You refused to marry my sister, so now I have to destroy your countryside.
TL;DR Varangians = Vikings who settled in Russia, attacked the Byzantine Empire, became Christian, then sent men to fight for the Byzantines because the Byzantine Emperor didn't trust his own people.
Crusades happened because European Christians were too busy fighting each other, the Pope wanted unity and more power, the Byzantines didn't want to lose anymore territory to the Turks or Arabs, and European Christians wanted lots of money and land.
