But that which has given Justinian's reign a greater distinction than any conferred upon it by brilliant military achievements, is the collection and publication, under the imperial direction, of the _Corpus Juris Civilis_, or "Body of the Roman Law." This work is the most precious legacy of Rome to the modern world. In causing its publication, Justinian earned the title of "The Lawgiver of Civilization" (see p. 358). In the midst of this brilliant reign an awful pestilence, bred probably in Egypt, fell upon the empire, and did not cease its ravages until about fifty years afterwards. This plague was the most terrible scourge of which history has any knowledge, save perhaps the so called Black Death, which afflicted Europe in the fourteenth century. The number of victims of the plague has been estimated at 100,000,000. THE REIGN OF HERACLIUS (A.D. 610-641).--For half a century after the death of Justinian, the annals of the Byzantine empire are unimportant. Then we reach the reign of Heraclius, a prince about whose worthy name gather matters of significance in world-history. About this time Chosroes II., king of Persia, wrested from the empire the fortified cities that guarded the Euphratean frontier, and overran all Syria, Egypt, and Asia Minor. What was known as the True Cross was torn from the church at Jerusalem and carried off in triumph to Persia. In order to compel Chosroes to recall his armies, which were distressing the provinces of the empire, Heraclius, pursuing the same plan as that by which the Romans in the Second Punic War forced the Carthaginians to call Hannibal out of Italy (see p. 264), with a small company of picked men marched boldly into the heart of Persia, and in revenge for the insults heaped by the infidels upon the Christian churches, overturned the altars of the fire-worshippers and quenched their sacred flames. The struggle between the two rival empires was at last decided by a terrible combat known as the Battle of Nineveh (A.D. 627), which was fought around the ruins of the old Assyrian capital. The Persian army was almost annihilated. In a few days grief or violence ended the life of Chosroes. With him passed away the glory of the Second Persian Empire. The new Persian king negotiated a treaty of peace with Heraclius. The articles of this treaty left the boundaries of the two empires unchanged.