In this chronology, I have tried to present the remarkable diversity of this astonishing period, covering events from the England of King John the Bad, to Byzantium during the period of the Fourth Crusade and its aftermath, to the Mongolia of Genghis Khan. Significant events in Byzantium during a given year are listed first in each entry, followed by events elsewhere.

1201: Kalojan of Bulgaria besieges and captures the cities of Constantia and Varna ( March). By the Treaty of Venice, the leaders of the Fourth Crusade agree to pay the Republic 85,000 silver marks for transporting them to the Holy Land. The Republic begins construction of the immense fleet necessary to transport the Crusaders. The protostrator Manuel Kamytzes is ransomed from a Bulgarian prison by his son-in-law, Chrysos of Prosakos. When Alexius refuses to repay Chrysos for the ransom money, Chrysos and Kamytzes rebel, capturing Pelagonia and Prilep and raiding the country as far as the Vale of Tempe. Alexius III releases Alexius, son of Isaac II from captivity so that he can accompany him on his campaign against Kamytzes; Alexius arranges with the master of a Pisan ship for a small boat to be sent to him, and by this means he escapes to the ship and thence sails to Sicily (September). He eventually continues on to Hagenau, where Philip of Swabia, another son of Frederick Barbarossa and the second husband of his sister Irene, is now ruling as King of Germany. Here he meets Boniface of Montferrat, one of the leaders of the Fourth Crusade (whose brother Conrad had been married to Alexius's sister Theodora). Leon Sgouros, Archon of Nauplia since 1198, rebels against Alexius III.

Az-Zahir of Aleppo again marches on Damascus, and persuades al-Afdal to join him in besieging their uncle al-Adil there (August). Al-Adil manages to subvert az-Zahir's vassals, however, and he is eventually forced to lift the siege (September).

1202: Alexius III captures Chrysos, and then makes peace with Kalojan of Bulgaria. Alexius IV travels to Rome and seeks the Pope's assistance in recovering his father's throne, but Innocent III rejects his claim and also prohibits Boniface of Montferrat from turning the Crusade against Christians (spring). The members of the Fourth Crusade arrive in Venice (June); however, fewer come than anticipated, and those who do can raise only 51,000 marks. The Venetians agree to forgive the remaining debt if the Crusaders assist them in the reconquest of the Dalmatian city of Zara, recently seized by the Hungarians. Alexis IV arrives in Venice and appeals for the assistance of the Fourth Crusade in recovering his father's throne from Alexius III. The Fourth Crusade sails from Venice (early November). Its initial target is Zara, which it recaptures from the Hungarians (11-24 November).

War begins between King John of England and Philip Augustus of France.

Az-Zahir of Aleppo and al-Afdal recognize al-Adil as supreme Sultan of the Ayubid Empire (late January).

The Mongol Temujin crushes the Tatars, who were responsible for the murder of his father.

1203: During an interlude on Corfu, Alexius concludes a treaty with the leaders of the Fourth Crusade, promising to support them with money and troops if they will restore him and his father to the throne of Byzantium (May). The Fourth Crusade arrives off Constantinople (early July). The Fourth Crusade seizes Constantinople (July 17); Alexius III flees the city, leaving his wife Euphrosyne behind to be imprisoned; the blinded Isaac II is reinstated as Emperor, along with his son, as Alexius IV. Alexius Ducas Mourtzophlos is released from prison and becomes protovestiarios to Alexius IV; however, he plots to undermine his position and supplant him. A party of Latins who were seeking to rob Saracen merchants set fire to their district, and the flames spread to a large portion of the city (August 19). Alexius IV and Boniface of Montferrat march through Thrace, driving Alexius III ahead of them and forcing the cities to pay tribute (August 19-November 11). On his return to Constantinople, Alexius IV hangs the conspirators who participated in the overthrow of his father (November). An ancient statue of Athena Parthenos which stood in the Forum of Constantine -- possibly that of Phidias which was originally placed in the Parthenon -- is destroyed by a superstitious mob that believes she is beckoning to the Latins.

King John murders his nephew Arthur of Brittany, who has been his captive, at Rouen (April). In response, Brittany revolts against John. Philip Augustus lays siege to Chateau Galliard, the great fortress built by Richard the Lion-Hearted on a bluff high above the Seine on the eastern border of Normandy (August).

Temujin completes his conquest of eastern Mongolia (fall). Death of Sultan Ghiyas al-Din of Ghor, who is succeeded by his brother Muizz al-Din as ruler of the Ghurid Empire.

1204: Isaac II and Alexius IV are deposed at a public assembly in Sancta Sophia (January 25); Alexius IV is seized and imprisoned (January 29); Alexius V Mourtzophlos becomes Emperor (early February); Alexius IV is strangled and Isaac II dies. The Crusaders agree to attack the city and provide that a college of twelve electors will select a new Latin Emperor if they are successful (March). Constantinople subsequently falls to the assault of the Fourth Crusade (April 9-12). Alexius V flees to Thrace when he realizes that the city is lost. Trebizond falls to the forces of David and Alexius Comnenus and Queen Thamar of Georgia, marking the start of the Empire of Trebizond (April). Boniface of Montferrat marries Isaac II's widow, Margaret-Maria of Hungary, in hopes of strengthening his claim to the throne of the Latin Empire. The Venetians prefer a more pliable candidate, however, so Count Baldwin of Flanders and Hainault is elected Latin Emperor of Romania (May 16). Boniface instead is authorized to take Thessalonica as the basis for a new kingdom in Greece, and he sells Crete (which he had received as a fief from Alexius IV) to the Venetians.

Alexius V, the Empress Euphrosyne, and her daughter Eudocia (Alexius's mistress) arrive at Alexius III's refuge at Mosynopolis in Thrace. Alexius III allows Alexius V to marry his daughter Eudocia, then seizes and blinds him (summer). Leon Sgouros marches on Athens and captures the lower city, but the acropolis holds out against him under the leadership of the city's archbishop, Michael Acominatus (summer).

Alexius V was captured by the Franks in late November, and was the sent to Constantinople to stand trial for the feudal crime of having deposed his lord (Isaac II) and put him to death by strangulation. With frankness and gallantry, if not tact, he defended himself on the ground that Isaac II and his son were traitors to the state. The court of Frankish barons convicted him and sentenced him to death, which was carried out by having him thrown down from the top of the Column of Theodosius in the Forum Tauri in Constantinople (December). Alexius III, wandering in Thrace, is captured by Boniface, who sends him to Montferrat to be held in prison (December). The Latin Emperor Baldwin and his brother Henry defeat the forces of Theodore Lascaris at Poimanenon in Bithynia (December 6).

Rukn al-Din dies, and his brother Kay-Khusraw, who has been living in exile in Byzantium, recovers his position as Seljuk sultan.

Philip Augustus's forces successfully undermine the outermost tower of Chateau Galliard (February), and the inner citadel soon falls to the French (March 6). Eleanor of Aquitaine dies at the abbey of Fontevrault in the Loire (April 1). Rouen falls to Philip (June 24). By July, all of Normandy is under Philip's control.

Innocent III commissions Peter de Castelnau and Arnold-Amalric, Abbot of Citeaux, as his legates with instructions to suppress the Cathar heresy in Provence, the Midi, and Languedoc. Temujin crushes the Naimans and kills their Tayang in a hard-fought battle near modern-day Karakorum, thereby securing the western part of Mongolia (late spring or summer).

In a series of three battles, Muizz al-Din initially defeats Shah Muhammad of Khwarazm, who rules two-thirds of Persia, but then is defeated by the Khwarizm and their Mongol Kara-Khitai allies at Hezarasp and Andkhoi, west of Balkh, where the Ghurid army is destroyed (September-October).

1205: Henry of Flanders, Baldwin's younger brother, leads an army into Asia Minor, where he captures Adramyttium and advances down the coast, defeating Greek forces led by Theodore Mangaphas of Philadelphia (winter-spring). Boniface of Montferrat marches with his army into central Greece, captures Thebes and Athens, and besieges Leon Sgouros, Archon of Nauplia, in the fortress of Acrocorinth (spring). War breaks out between the Latin Empire and the Bulgars under Kalojan, who advances into Thrace and takes Adrianople, calling on the Byzantines to revolt against the Latins (March-April). The Latin Emperor Baldwin, accompanied by Doge Dandolo, marches with the rest of his army against Adrianople, but his force is overwhelmed and destroyed by the Bulgars (April 14); Baldwin is captured and later executed by Kalojan. Doge Dandolo of Venice dies in Constantinople (June).

David Comnenus occupies Paphlagonia and then sends an army against Nicomedia, which is held by Theodore Lascaris, but Lascaris ambushes it and captures its commanding general, thereby setting a limit to the westward advance of the Trapezuntine Empire. At the same time, David's brother Alexius is besieging the port of Amisos on the Black Sea, which is still under the rule of its Byzantine Governor, Sabbas. Sabbas appeals for assistance to Sultan Kay-Khusraw of Iconium; he marches to the relief of Amisos, and routs Alexius Comnenus and his troops in a battle fought beneath the city walls. William of Champlitte and Geoffrey de Villehardouin defeat Greek forces led by Michael Ducas of Epirus at Koundoura in Messenia, thereby winning control of most of the Morea (summer-fall).

Chinon in the Touraine falls to Philip, completing his conquest of the English possessions in France north of the Loire.

Ikhitiyar, Ghurid Governor of Bijar and Bengal, attempts to conquer Tibet, but the campaign ends disastrously and he is murdered the following year.

1206: Theodore Lascaris, son-in-law of Alexius III, establishes the Empire of Nicaea. Henry of Flanders, who has been serving as Regent, is formally enthroned as Latin Emperor (August).

In a mass assembly of the Mongol peoples near the headwaters of the Onon River, Temujin is proclaimed the Great Khan (Genghis Khan) of all the Mongols (spring).

Muizz al-Din dies (March 13). The Shah of Khwarazm conquers Herat and Ghor from the Ghurid sultanate.

1207: Sultan Kay-Khusraw of Iconium seizes Attaleia from Aldobrandini, an Italian mercenary captain who captured the city in the confusion after the fall of Constantinople. King Boniface of Thessalonica is killed in a battle with the Bulgars (September 4). Kalojan of Bulgaria is murdered while besieging Thessalonica (October 26); he leaves only an underage son to succeed him, and Kalojan's nephew Boril soon usurps the Bulgarian throne.

When Count Raymond VI of Toulouse refuses to comply with their demands, the papal legates Peter de Castelnau and Arnold-Amalric of Citeaux order the Count excommunicated, form a league of the Count's orthodox vassals against him, and place his lands under interdict. Innocent III offers the benefits of a crusade to Philip Augustus and his vassals if they will take up arms against Raymond on behalf of the Church. Raymond agrees to yield.

Muhammad of Khwarazm establishes his suzerainty over Bukhara and Samarkand, which previously paid tribute to the Mongol Kara-Khitai.

1208: (Easter) Theodore Lascaris is crowned as Emperor of Nicaea by the Orthodox Patriarch Michael Autorianus (early April). Leon Sgouros, having endured three years of siege atop the Acrocorinth, is overwhelmed with despair and commits suicide by leaping his horse over the mountain's cliffs. Michael Ducas of Epirus sends his half-brother Theodore to take over the Acrocorinth's defense. The Latin Emperor Henry defeats a raid by Boril of Bulgaria, then secures Thrace and captures Philippopolis (summer). He then marches on Thessalonica, now ruled by a committee of Boniface's former barons as regents for Boniface's young son Demetrius.

The papal legate Peter de Castelnau is assassinated by one of Raymond VI's vassals (January). On learning of de Castelnau's assassination, Innocent III renews Raymond's excommunication, absolves his vassals from their oaths of obedience, and has the crusade preached in northern France (March).

The nave of the cathedral of Notre Dame in Paris is completed. Frederick II, the Wonder of the World, is declared of age (at 14), is crowned King of southern Italy and Sicily, and marries Constance of Aragon (December).

1209: The Latin Emperor Henry of Flanders compels the barons of the Kingdom of Thessalonica to acknowledge his suzerainty, and appoints his brother Eustace as regent for Boniface's young son. Michael Ducas of Epirus also agrees to recognize Henry's suzerainty and marries his daughter to the Regent Eustace. Henry and the Seljuk Sultan Kay-Khusraw form an alliance against Theodore Lascaris of Nicaea.

Just as it appears that Philip of Swabia has defeated Otto IV in the German civil war, Philip is murdered by Count Otto of Wittelsbach as a result of a private grudge (June 9). Otto IV enters Italy and is crowned as Holy Roman Emperor (October).

The barons and prelates of northern France assemble with their troops at Lyons to embark on the Albigensian Crusade against the Cathars of Languedoc and Provence (June). Raymond VI makes his submission to the papal legate, so the crusade continues against the lands of Raymond's nephew Raymond-Roger of Trencavel, Viscount of Beziers and Carcassone. Under the leadership of Simon de Montfort, the Crusaders storm Beziers and massacre Catholic and Catharan inhabitants alike after a bishop orders Kill them all: God will know his own (July 22). Following a two-week siege, Carcassone surrenders (August 15), but the populace is allowed to leave; Raymond-Roger is taken captive and dies a few months later. Narbonne and other towns surrender.

While listening to the reading of the gospel in the chapel of Santa Maria degli Angeli, Francis of Assisi, who has been living as a hermit and tending lepers since his conversion several years earlier, realizes that his real vocation to go forth and preach the gospel to all whom he encounters. He then begins laying plans for an organization of itinerant preachers that will become known as the Franciscan Order.

1210: Geoffrey de Villehardouin becomes Prince of Achaea (March). Following a five-year siege, the Acrocorinth falls to the Franks; Theodore Ducas escapes to Argos (autumn). St. Francis of Assisi submits the first version of what will become the Rule of the Franciscan Order to Pope Innocent III for his approval. The Order of the Friars Minor grows rapidly in the following years.

In a battle fought on either the Ilamish or the Talash steppe, Muhammad of Khwarazm defeats a Kara-Khitai general sent to recover Samarkand.

1211: Sultan Kay-Khusraw pushes down the Meander Valley, accompanied by Alexius III, who arrived at his court the previous year after being ransomed by Michael I Ducas of Epirus. His army is defeated and he is personally slain by Theodore I Lascaris (late spring). Alexius III is captured by his son-in-law Theodore Lascaris, who allows him to spend the rest of his life in a monastery. Kay-Ka'us succeeds his father as Sultan of Iconium. The Franks capture Nauplia. Theodore Lascaris is defeated on the river Rhyndacus by the Latin Emperor Henry (October 15).

The Emperor Otto IV invades the Kingdom of Sicily and conquers Apulia, but a rebellion in Germany fomented by Innocent III and Philip Augustus of France compels him to return home before he is able to finish his conquest of Frederick II's kingdom.

After Raymond VI refuses to meet the demands of the Council of Montpellier (January-February), Simon de Montfort and the Albigensian crusaders attack Raymond VI's domain. However, they fail to take Toulouse (late June).

The heiress Clara of Assisi and other women sympathizers of Francis's form a communal colony that lives at the chapel of St. Damian outside Assisi's walls.

Genghis Khan begins his conquest of northern China, which will continue until his death in 1227.

1212: The citadel of Argos falls to the Franks (summer). The Venetians conquer Crete from the Genoese Enrico Pescatore, who has held it since 1208.

Frederick II travels to Germany. South Germany goes over to him, and he is crowned as a rival Emperor to Otto IV by the Archbishop of Mainz (December).

After a shepherd boy named Stephen has a vision of Jesus in the Vendome (June), a curious religious hysteria sweeps France and Lorraine, and bands of children begin to march towards the Mediterranean ports, saying that they are seeking God. Somewhat earlier, in May, bands of children begin to assemble in the Low Countries and the Rhineland. Eventually, a great procession, animated by a rumored prophecy that they will recover the Holy Land from the Saracens, marches up the Rhine, over the Alps, down into Lombardy, and thence to Genoa (August 25) where, finding no ships to take them the rest of the way, their crusade – known to history as the Children's Crusade – breaks up and disperses.

King Alfonso VIII of Castile (accompanied by Peter II of Aragon) crushes the army of the Almohads at Las Navas de Tolosa in the greatest Christian victory of the Reconquista (July 16). This victory results in the Christian reconquest of all of southern Portugal and most of southern Spain between Valencia and Seville, leaving to the Moslems only a mountainous redoubt centered on Granada. It also leaves Peter free to intervene more forcefully in the Albigensian war against his vassal, Count Raymond VI of Toulouse.

Uthman of Samarkand revolts against Muhammad of Khwarazm. Muhammad marches on Samarkand, captures and sacks it, and executes Uthman.

1213: King Peter II of Aragon, although orthodox, intervenes in the Toulousain war on Raymond VI's behalf in his capacity as his suzerain. The Albigensian crusaders, under the command of Simon de Montfort, surprise and defeat the vastly superior forces of Count Raymond and King Peter at Muret (September 12); Peter is killed in the fighting and his son James I is captured. De Montfort is soon recognized as Count of Toulouse and Duke of Narbonne. [In 1218, Toulouse revolts and de Montfort is killed trying to recapture the city.]

1214: The Latin Emperor Henry of Flanders and the Nicene Emperor Theodore Lascaris sign the Treaty of Nymphaeum after eight years of intermittent fighting.; the Latin Empire is recognized in possession of northwest Asia Minor as far as Adramyttium. Theodore Lascaris then attacks David Comnenus, the Trapezuntine Emperor Alexius's younger brother, in Paphlagonia and conquers Heraclea and Amastris. At the same time, the Seljuk Sultan Kay-Ka'us marches on Sinope, the largest city under David's control. David marches to defend it, but is killed in a battle with the Turks outside the city. Alexius Comnenus hastens to Sinope and retakes it, but is then captured by the Sultan's troops outside the city. To win his freedom, Alexius agrees to surrender Sinope and become the Sultan's vassal. The Despot Michael Ducas of Epirus conquers Corfu from the Venetians.

Philip Augustus of France defeats a German and English army under Otto IV at Bouvines in Flanders (July 26), one of the decisive battles of the world according to the Cambridge Medieval History, spelling a final end to King John's hopes of reconquering his former possessions in Normandy and the Loire. Otto IV rapidly loses support in his civil war against Frederick II following his defeat; he is practically without supporters and controls little territory when he dies four years later (May 19, 1218).

Raymond, eldest son of Bohemond III of Antioch, is murdered by the Assassins at Tortosa.

1215: Michael Ducas of Epirus is assassinated. He is succeeded by his half-brother Theodore.

In the Fourth Lateran Council (November), Innocent III declares that Otto IV is deposed and Frederick II is confirmed as Holy Roman Emperor. Frederick agrees to take the cross and go to the Holy Land as a crusader. The Council also declares that Raymond VI of Toulouse is dispossessed of his lands for having harbored heretics, and Simon de Montfort is to be invested with his lands and title.

The Mongols under Genghis Khan capture Peking following a short siege. The inhabitants are massacred and the city is burned to the ground after a sack lasting an entire month (spring).

The English barons, aided by Stephen Langton, Archbishop of Canterbury, compel King John to sign the Magna Carta at Runnymede on the Thames (June 15).

1216: The Latin Emperor Henry of Flanders dies at Thessalonica while preparing a campaign against the Bulgars (spring). Death of Pope Innocent III (summer). Death of King John of England (October).