Apart from the Fourth Crusade, which was really unmatched from a pure irony perspective, the Second Crusade (caveat that the whole Crusade numbering thing is really a modern historian’s conceit and not an actual historical phenomenon) can make a serious claim to being the Crusadiest Crusade of them all. It started off with noble goals, completely fell apart in the planning stage, failed entirely in its intended mission, and then fizzled out for good in a battle it had no real business fighting. Called by Pope Eugenius III (d. 1153) in December 1145 (and then again in March 1146), it was supposed to amass an army to head off and relieve the Crusader states from the pressure they were feeling from a Turkic dynasty called the Zengi. Imad al-Din (“Pillar of the Faith”) Zengi (d. 1146) founded this dynasty by getting himself appointed governor of the cities of Aleppo and Mosul on behalf of the Great Seljuk Empire in the 1120s, then turning his dual governorship into a hereditary position by virtue of the fact that the Seljuk empire was too weak to stop him even if it wanted to (lots of local governors were getting away with this at the time, not just Imad al-Din).
Imad al-Din spent what seems like an unhealthy portion of his life trying to add Damascus to his burgeoning little kingdom, but the governors of Damascus always managed to keep him at bay, so in 1144 he decided to take a break from trying to conquer Damascus and pick of some lower-hanging fruit: the Crusader County of Edessa (in modern Turkey, in the upper Euphrates region). It was that conquest, the first major Crusader defeat since the capture of Jerusalem in 1099, that panicked Pope Eugenius enough to get him to call for a new Crusade. Imad al-Din was assassinated in 1146 after at least one more attempt to capture Damascus, and for a brief time the Count of Edessa, Jocelin II, was able to retake his County, but he was quickly driven out again by Nur al-Din Zengi (d. 1174), Imad al-Din’s son and his heir in Aleppo (Nur al-Din’s brother Saif al-Din inherited Mosul).
The Crusade amassed what should have been a heck of an army, mostly on the strength of a charismatic Cistercian preacher named Bernard of Clairvaux (d. 1153), who changed the rhetoric of the First Crusade (where participants had been promised spiritual rewards for aiding the Byzantines and capturing Jerusalem) to make participation in the Crusade itself, not the successful completion of its goals, the path to those rewards. Since Jerusalem was still in Christian hands, there really was no goal left in the East that could have enticed a bunch of European knights to risk their lives for it, but making the campaign itself a holy act seemed to do the trick. Bernard barnstormed Europe preaching about the importance of the Crusade, as Peter the Hermit had done for the First Crusade. Just as Peter did, Bernard found lots of knights ready to take the cross, and lots of good Christian folk who couldn’t afford to go to the Holy Land, but were happy to go torch a Jewish neighborhood or two and kill all the Jews living there instead, even though Bernard seems to have repeatedly told people not to do that sort of thing. As Chris Rock said, “that train’s never late.”
Most importantly for Bernard, Louis VII of France (d. 1180) agreed to go on crusade, so the campaign was assured of having at least one major monarch and one major army. One ruler the Pope didn’t want making the Crusade was Conrad III, the Holy Roman Emperor (d. 1152), because Eugenius was relying on him to defend Rome from the Norman King Roger II of Sicily (d. 1154). But you know, once the preaching gets started, you can’t control where it goes, so before long Germany was rife with Crusading fever, and Conrad, though reluctant to agree, finally gave in when Bernard (who eventually decided that Eugenius could get bent and went after Conrad despite papal orders against it) leaned hard on him about it. Roger actually offered to transport the armies to the Holy Land, on the condition that they make one tiny side trip to sack Constantinople and let Roger take most of the booty home with him. Louis passed on that offer.
Things got off to catastrophic start when Conrad made it to Constantinople on September 10, 1147, before Louis. The Byzantines, ruled at the time by Emperor Manuel I Komnenos (d. 1180) were pretty pissed at the whole idea of the crusade. Why, you ask? Well, for one thing, the First Crusade had been a complete bust from their perspective; it had captured Jerusalem, sure, but that didn’t help the Byzantines, and the Crusaders had done virtually nothing to alleviate the Seljuk threat that Constantinople was facing. For another thing, the Byzantines were actually on OK terms with the Seljuks at the time, and they didn’t want the Seljuks attacking their territory because of the Crusaders. And last but not least, if Conrad was on Crusade that meant that he wasn’t helping Manuel and Eugenius to alleviate their collective Norman problem. So the Byzantines weren’t interested in housing and supplying a Crusader army that offered them nothing but problems. Instead of waiting for Louis to arrive so they could cross into Asia together, which would have been, you know, smart, Conrad and Manuel seemed to mutually agree that the Crusaders should shove off ASAP.
Conrad figured he would follow the same route as the First Crusade, which would have taken his army to Edessa while, so he thought, passing much of the way safely in Byzantine territory. He was so confident of his plan that he even divided his army and put half of it under the command of his brother, Otto, so that Conrad and the stronger knights could take the harder but faster overland route while Otto and the weaker forces could take the safer but longer coastal one. This was a huge mistake. On October 25, Conrad’s army met the Seljuks at Dorylaeum, in northwest Anatolia, and it was virtually annihilated. Otto’s force met a similar fate a few months later. So a little over a month into the campaign, half of the Crusader army was off the board.
Louis arrived in Constantinople in early October and was comparatively treated pretty well by Manuel, who wasn’t personally angry with Louis the way he was with Conrad. He crossed into Asia and met with Conrad, who had almost no forces at all, and together they headed toward Jerusalem. Conrad took ill along the way and went back to Constantinople, while Louis’ forces were constantly harassed both by the Seljuks and by the Byzantines, whose forces were on alert to protect Byzantine subjects from the Crusaders. Finally Louis got tired of marching overland and tried to hire ships to ferry his army to Antioch, but he just couldn’t find enough ships for the job. So he loaded clergy, nobles, and of course himself on to the ships, left some money on his army’s nightstand, and said “hey, see you guys in Antioch,” before taking off. He got to Antioch alright, but the army was massacred by the Seljuks at the Battle of Mount Cadmus, near Laodicea (in southwest Anatolia), on January 6, 1148. Now the other half of the army was off the board, and there was no chance of retaking Edessa from the Zengis.
Raymond of Antioch, the uncle of Louis’ very rich wife, Eleanor of Aquitaine, saw a way to salvage this disaster by putting Louis’ remaining troops, and especially his money, in the service of a campaign to capture Aleppo, and he convinced his niece to threaten annulment if Louis refused. Louis had her arrested and sailed for Jerusalem instead, where he was joined by Conrad (who had hired a mercenary army) and some additional knights from France. In June 1148 they decided to attack Damascus. Damascus, despite being a Muslim city, had been allied with the Crusaders since the days when they were fending off Imad al-Din, but the Crusaders feared, probably correctly, that the city was on the verge of falling into Nur al-Din’s hands. So on July 24, 1148, they laid siege to Damascus, the former capital of the Umayyad Caliphate and one of the grandest cities in the Islamic world.
The Crusaders managed not to do anything stupid for a whole three days, but on July 27 they decided almost inexplicably to give up their well-defended position to try to attack the city from the east, where they thought the walls were weaker but where their own forces would be exposed on an indefensible plain without easy access to water. They were finished within a day, and by July 29, today, the army, or what was left of it, had limped back to Jerusalem. Conrad left immediately, but Louis stayed behind to try to see if he could wring something positive out of this experience, or at least keep his marriage together. He failed on both counts.
In a way, the Second Crusade laid the groundwork for the Fourth Crusade; Louis was so angry at the Byzantines by the time he finally did go back to France that he proclaimed that he and the Normans were going to take a new Crusade against Constantinople. While they never got any support for this, as Crusades historian Thomas Madden writes in his The Concise History of the Crusades (my pick if you’re looking for a single-volume history of the Crusades), “the perception that the Byzantines were part of the problem rather than the solution became widespread.” Bernard of Clairvaux spent the rest of his life blaming the sins of the Crusaders for the failure of the Crusade, which I guess is fair if you consider “dumb” to be a sin. Eleanor got her annulment and wound up marrying Henry II of England, as fans of James Goldman plays will already know.
Again, the Fourth Crusade is obviously the peak of Crusade absurdity, but the Second Crusade takes the prize for squandered potential. Conrad and Louis together could have had the strongest army the Crusaders ever assembled, and they were campaigning at a time when the Seljuks were undeniably on the decline (the Great Seljuk Empire would be gone by the end of the century and its component kingdoms would be Mongol vassals within another ~50-60 years) but they blundered the whole campaign away in a fog of political backbiting and poor decision-making.