Leo VI completed the recodification of Roman law in Greek, wrote on tactics and ceremony, married four times to produce an heir, and lost Sicily, Thessalonica and every war he fought.
Leo VI ruled from 886 to 912 and is the most bookish emperor between Constantine VII and nobody at all — his own grandson would be the next.
He completed the Basilika, the sixty-book Greek recodification of Justinian's law that his father had begun, and wrote or sponsored the Taktika on warfare, the Book of the Eparch on the guilds of the capital, homilies, and poetry.
He also lost Sicily, saw Thessalonica sacked, was beaten repeatedly by Symeon of Bulgaria, and spent the last decade of his reign in a canonical crisis of his own making over his fourth marriage.
He was born in 866 to Eudokia Ingerina, who had been the mistress of the emperor Michael III before Basil I married her at Michael's arrangement. Whether Basil or Michael was his father was asked in his own lifetime and cannot be answered.
Basil disliked him, and in 883 imprisoned him for three years on a charge of conspiracy, releasing him only shortly before his own death.
He was educated by the patriarch Photios, the outstanding scholar of the age, and the education took: the reign's intellectual output is real and much of it is his own work.
He is a genuinely odd figure — a scholar-emperor with no military ability, a legislator on marriage who broke his own law, and a ruler whose most famous act was a canonical scandal.
The sources treat him with a kind of baffled respect. His learning is not in question; his judgement of people was poor and his judgement of Symeon of Bulgaria was catastrophic.
The marriages define him. Three wives died without leaving a surviving son, and Byzantine canon law regarded even a third marriage as barely tolerable. He took a mistress, Zoe Karbonopsina, she bore him Constantine, and he married her — a fourth marriage, uncanonical beyond argument, which got him barred from communion and split the church into factions that outlasted him.
The Basilika is the achievement. Sixty books, in Greek, superseding the Latin corpus that had become unusable, and remaining the law of the empire until its end. Alongside it he issued the Novels, over a hundred new laws, several of which quietly abolished dead letters — including, with some irony, provisions on marriage.
The wars went uniformly badly. Symeon of Bulgaria beat Byzantine armies repeatedly from 894 and extracted tribute; Thessalonica, the empire's second city, was sacked from the sea in 904 by a renegade fleet under Leo of Tripoli; and Taormina fell in 902, completing the Muslim conquest of Sicily.
His Taktika, written while all this was happening, is a serious and intelligent treatise on how to fight the empire's enemies. The gap between the analysis and the results is the reign in one image.
The legal codification outlasted everything else and is the reason the Macedonian period is remembered as a legal as well as a military high point.
The fourth marriage got him his heir, and Constantine VII produced the books this archive relies on and the dynasty that produced Basil II. Judged on that alone the scandal was worth it, which is presumably how he judged it.
The Hagia Sophia mosaic over the Imperial Door, showing an emperor prostrate before Christ, is generally identified as him. If so it is a striking piece of self-presentation from a man the church had barred from communion — the emperor on the floor, asking.