A Dictionary of Greek and Roman biography and mythology

Ἰωάννης, Latin emperor of Constantinople,the third son of Everard, count of Brienne, and Agnes, countess of Miimpelgard, was born in 1148. He was one of the leaders of the Latins who took Constantinople in 1204, and in 1210 was chosen king of Jerusalem, which was then in the hands of the Turks. In 1218 he commanded the famous Latin expedition against Egypt, and made himself so conspicuous, through his military skill and undaunted courage, that he was looked upon as the greatest hero of his time. It was for this reason that in 1228 the Latins of Constantinople chose him, though he was then merely titular king of Egypt, to govern for the minor emperor, Baldwin II.; and in order to strengthen his authority, they invested him with the title and power of emperor. Although 80 years old, John accepted the offer, but first went to Europe to levy troops, with which he arrived at Constantinople in 1231, where he was crowned with great solemnity, and pleased both the Latins and Greeks by his majestic appearance (he was the tallest man they had ever seen) and his energetic administration. Not only unbroken by age, but still uniting the strength of a powerful man with the agility of a youth, he defended Constantinople with great success against the united armies of Asan, king of Bulgaria, and John Vatatzes, the Greek emperor of Nicaea, as is narrated in the life of the latter. [JOANNES III.] Constantinople would have fallen but for him. Marvellous stories are told of his bravery and the power of his arm. After a reign of nine years John of Brienne died in 1237, leaving several sons; but he was succeeded on the throne of Constantinople by Baldwin II. A daughter of John of Brienne was married to the emperor Frederic II. of Germany. [JOANNES III.; BALDUINUS II.] (The sources quoted in the lives of these two emperors; Du Cange, Histoire de Constantinople sous les Empereurs Français, p. 88, &c.)

[W.P]