Well, I don’t know about that, the Mongols never got further west than Poland. Everything Europe had learned from the Crusades, it got to keep.
One thing that the Crusades did was severely weaken the Byzantine Empire, with a Catholic coalition even sacking and occupying Constantinople for several years. The Byzantines never recovered, and were no match for the Ottoman Turks who rose to power soon after the Crusades ended. An Empire capable of resisting the Turks would have meant a very different history for Asia Minor, the Balkans and the Middle East.
One of the lasting effects of the Crusades was to bring Europe to an awareness of the world beyond its shores–a world which at that time was wealthier, more open to commerce, and more scientifically advanced.
The Crusades stimulated a tremendous interest in the products of the East–silk, spices, gems, medicines, perfumes. In the short run this stimulated production and commerce as Europeans sought to buy these products via overland trade through many middlemen. Later on, desire to go the source stimulated the Age of Discovery.
Europe was also philosophically enriched by contact with the East–from Hindu-Arabic numerals to the recovery of classical works of science in Arabic translation.
The Crusades and the contemproaneous Mongol invasion from the East seemed to have the opposite effect in the Arabic world–the Arabs hunkered down and became less open to outside influence and more scientifically and philosophically stagnant.
“what were the long term effects of the Crusades?”
It’s too soon to say.
The Crusades were very useful in supplying today’s Islamist apologists with another justification to guilt trip the west and make us think we somehow deserve to have a dozen humour writers at Charlie Hebdo shot in cold blood by murderous thugs. I was in Europe when this occurred and I could not believe how quickly Muslim commentators were in print and on the airwaves to say, "Ahem, of course this shooting was terrible, but let’s not forget (here launch into an endless recitation of the sins of the west against Islam, starting with the Crusades.)
The southern branch of the Mongols wiped out Persia and the Caliphate of Baghdad, and Tamerlane got as far as Damascus. They pretty much annihilated the high Islamic civilization of the time. That pretty much overwhelms what little effect the Crusades had.
True (although I don’t really consider empires that only last 1 guy’s lifetime to be truly worthy of the name “Empire”…)
To be fair, his empire was so big that it when it split, the pieces were big enough to be called empires themselves - and they lasted for centuries.
But the First Crusade was only called because Alexios Komnenos wrote to Urban II asking for help against the Turkish hordes. You could equally well argue that the Crusades helped *extend *the lifespan of the Byzantine Empire. Not least by giving the locals someone else to fight first.
Various Greek states owned a number of distant colonies on several occasions. For example, (parts of) Sicily was colonized successively by Phoenicia, Carthage, (itself a colony of Phoenicia), and, eventually Corinth. As a result of the Peloponnesian War, Carthage made another bid to colonize Sicily, but was eventually beaten back, leaving Sicily, more or less, to Syracuse (which then colonized southern Italy while fighting off subsequent attacks by Carthage), until Rome wandered down to take control of the whole area.
Further, as already noted, the Crusader lands in the Levant hardly considered themselves to be anything other than independent states and I do not recall France or other European powers declaring “ownership” of the lands in the Levant.
Greek colonies were supposed to show some deference to their founder-cities, but they weren’t really “owned” by them.
There was the “Athenian Empire”, but I’m not sure that really counts as a real Empire, since almost everyone in it was in the same ethnic group (Ionian Greeks) and lived in a pretty limited range.
Carthage probably counts as an empire though. They controlled their colonies directly, and the people under their rule included sizable numbers of non-Phoenicians.
That was allegedly in revenge for Persians comming the other way! 
Yes, but the Crusaders didn’t actually help; they sacked Constantinople more thoroughly than the Turkish hordes ever would have.
The rise of Venice (as well as Genoa, Milan, Florence…), as both poles of culture and economic powerhouses. Many crusaders hopped on their boats there, then came back bringing back books from the Levant ; and Italian principalities established commercial outposts all over the place, making a killing re-selling exotic goods and cornering the Silk Road.
It also led to the rise of banking as we know it, because while travelling to the Levant with a large bag of gold was ever so slightly on the unsafe side, you could stash a bag of cash at a Templar or Lombardian bank in Europe, get a letter of credit in return, go to the Levant and turn it into moolah over there.
Another long-term effect, of the Fourth crusade in particular : the lasting split between Catholics and Orthodox churches and people. Not that they had ever been super close, but when you burn and plunder the city that called for your help in the first place, they won’t ever give back the lawnmower.
That pretty much overwhelms the effect the Crusades had on Dar al-Islam – but not the effect the Crusades had on Christendom.
The question, however, is whether ordinary commerce, without the Crusades, might have done the same. Perhaps not. Probably not to nearly the same extent.
Q: What are the long term effects of the Crusades?
A: Such diverse elements as: fear, surprise, ruthless efficiency, an almost fanatical devotion to the Pope.
…and nice red uniforms.
I recall reading somewhere that the effect was the opposite: The crusades had the effect of removing those members of the nobility that were fanatically loyal to the pope and allowing more moderate nobles to take their place.
One long-term effect – pissing off Fox News when it’s brought up as an example of past Christian barbarity.
I’ll chalk this one up in the “positive” category.
This is what I came in to mention - the whole movement of scholasticism started with the recovery of the works of Aristotle and others.
This was hardly an unmixed blessing, because they tended to think that if it wasn’t in Aristotle, it couldn’t be real, but it was a path out of the Dark Ages into at least a distant relation of true learning.
Regards,
Shodan
Again, the question is whether ordinary commerce between Europe and the MENA, without the Crusades, might have done the same.