The Holy Roman Empire to the death of Barbarossa, the briefest of histories of Norway, Denmark and Spain, and the 4th Crusade. It's action packed.
The Investiture Crisis - Gregory VII and Henry IVth
Hildebrand, or Gregory VIIth to use his Papal name, was a reformer and Pope between 1073 and 1085. He firmly believed that the church should be independent from the influence of the material world, and unlike other Popes before and after him he was not prepared to compromise. He believed that the Papacy should be free of the influence of the Emperor, and indeed superior.
Henry IVth meanwhile was the descendant of Otto the Great. He believed in a system based on what he saw as the ancient right of the Roman Emperor to appoint the Pope. The system of government he inherited depended on him being able to choose churchmen he could trust to help him govern. He was utterly convinced in his right to 'invest' bishops and churchmen with the symbols of their office.
fought to establish their independence and liberties within the rule of the Emperor. In the struggle's most dramatic moment, beset by rebels allied with Gregory, Henry camped outside Gregory's palace in Canossa, in the robes of a penitent and pleaded to be accepted back into the Pope's favour. Gregory was forced to accept, and by so doing betrayed the rebels, who were then crushed by Henry. The Emperor established his own anti-Pope and ejected Gregory from Rome, who dies in exile in Sicily, lamenting
I have loved justice and hated iniquity - and therefore I die in exile
Frederick Barbarossa, Holy Roman Emperor, 1152 - 1190
Gregory thought he had lost - but in fact the long term victory was his. The Emperor's anti-pope was never accepted, and the idea of the Emperor's supremacy over the Pope lost. Despite the outward glory of Barbarossa's reign, in fact by the end of his reign the basis of the Emperor's power was sorely eroded. Frederick lost control of the northern Italian cities. he was forced himself to prostrate himself before Pope Alexander III. He held enormous power in Germany, but at the cost of a new deal with the German nobility that accepted that they were a closed, hereditary circle, with power over their own lands, while the Emperor remained elective. Under Emperors weaker than Barbarossa, the weakness of the Emperor's real power would be exposed.
Medieval Spain and La Reconquista
Spain had been largely overrun by the Arabs by the 9th Century, leaving 3 small Christian states surviving in the north - Leon in the North West, Navarre in the north and Aragorn in the north east.
By 1210, and the map shows, Spain was once again largely Christian, though far from completely. Despite periodic setbacks as new Caliphates tried to re-establish the old Islamic dominance, such as the Almoravids and Almohads, disunity among the Arab states allowed the kingdom of Castille to lead the fight back. The fall of Toledo in 1085 and victory at the battle of Las Navas de Tolosa in 1212 would prove decisive. By 1252, the last Muslim kingdom of Granada was a vassal of Castille, and would finally cease to exist in 1492.
After the death of Emperor Manuel Comnenos it is hard to find a Byzantine Emperor of any great talent. But the event which tore the heart out of the Empire came not from the East and the Islam world, but from the Christian west.
The evil genius is Enrico Dandolo, the Doge of Venice. Enrico uses the fee he is owed from transporting the Crusaders to force the crusade away from the objective of Egypt to first recapture the city of Zara. Then Alexius Angelos, a man with a claim to the throne of Byzantium, and persuades the Crusaders to help him gain the throne - for a fee of course. But once in place, he changes his mind about the fee - having looked first at the state of the Imperial treasury. As a result, the Crusaders attacked and took Constantinople, and submitted it to the traditional 3 day sack.
Here's a contemporary account which gives a flavour of the sacking:
How shall I begin to tell of the deeds wrought by these nefarious men ! Alas, the images, which ought to have been adored, were trodden under foot ! Alas, the relics of the holy martyrs were thrown into unclean places ! Then was seen what one shudders to hear, namely, the divine body and blood of Christ was spilled upon the ground or thrown about. They snatched the precious reliquaries, thrust into their bosoms the ornaments which these contained, and used the broken remnants for pans and drinking cups,-precursors of Antichrist, authors and heralds of his nefarious deeds which we momentarily expect. Manifestly, indeed, by that race then, just as formerly, Christ was robbed and insulted and His garments were divided by lot; only one thing was lacking, that His side, pierced by a spear, should pour rivers of divine blood on the ground.
Nor can the violation of the Great Church be listened to with equanimity. For the sacred altar, formed of all kinds of precious materials and admired by the whole world, was broken into bits and distributed among the soldiers, as was all the other sacred wealth of so great and infinite splendor.
When the sacred vases and utensils of unsurpassable art and grace and rare material, and the fine silver, wrought with gold, which encircled the screen of the tribunal and the ambo, of admirable workmanship, and the door and many other ornaments, were to be borne away as booty, mules and saddled horses were led to the very sanctuary of the temple. Some of these which were unable to keep their footing on the splendid and slippery pavement, were stabbed when they fell, so that the sacred pavement was polluted with blood and filth.
For Venice it was a triumph - they captured the right to the trade of the Empire. For Byzantium it was a disaster.
The Empire split into a small Latin Empire and several Greek Empires - as you can see from the map below. Although the Latin Empire lasts only 57 years, and is eventually reconquered, Byzantium never recovers its strength.