The global environmental cooling seen in the year 540 is probably due to a comet impact, evidenced by global tree ring growth diminution.

(Baillie, M.G.L.

(2007).

Tree-Rings Indicate Global Environmental Downturns that could have been Caused by Comet Debris, Chap.

5 in Bobrowsky, Peter T. and Hans Rickman (eds.

), Comet/Asteroid Impacts and Human Society: An Interdisciplinary Approach, Springer-Verlag, Berlin.

ISBN 3-540-32709-6, pp.

105–122.)

Khosrau has built defensive walls on the frontier against the Romans and their Arab allies in the Syrian Desert, against the peoples of the steppes of southern Russia at the town of Derbent between the Caucasus Mountains and the Caspian Sea, and to the east of the sea in the present Turkmen steppes.

The army does not remain on the defensive, however: Khosrau's reign is noted for his wars against the Romans.

Jealous of Justinian's victories in the West, Khosrau receives an embassy from the Ostrogoths at Ctesiphon, urging him to act before the Romans become too powerful.

Fearing Constantinople’s growing strength and intolerance of Zoroastrianism, he invades Syria in 540, breaking the “eternal” peace concluded eight years earlier.

The Persian army marches up the River Euphrates and follows a path to extract tributes from towns along the way to Antioch, the Empire’s third largest city.

Following the devastation of the earthquake of 526, Justinian I had renamed Antioch Theopolis ("City of God") and restored many of its public buildings.

The city had suffered another earthquake in 539, but the destructive work is completed by Khosrau I, who captures Antioch after a fierce siege, and systematically plunders the city to the extent that marble statues and mosaics are transported to Persia.

Antioch loses as many as three hundred thousand people.

For that the short time that he holds the city, Khosrau will take care, however, to protect the rights of Christian and Jewish minorities.

The Hephthalite king Toramana had broken through the northwestern defenses of the Gupta Empire in the 480s; by 500, the Huna, or Indo-Hepthalites, had overrun much of the empire, which had disintegrated under the attacks of Toramana and his successor, Mihirakula.

The Huna have conquered several provinces of the empire, including Malwa, Gujarat, and Thanesar, which have now broken away under the rule of local dynasties.

It appears from inscriptions that the Guptas, although their power has been much diminished, continue to resist the Huna and, in alliance with the independent kingdoms, drive the Huna from most of northern India by the 530's.

The succession of the sixth-century Guptas is not entirely clear; Vishnugupta, reigning from 540 in Bengal, is the last recognized ruler of the dynasty's main line.

The Himyarites had decided to establish a vassal state to control Central and North Arabia when the Adnani tribes of northern Arabia became a major threat to the trade line between Yemen and Syria in the fifth century.

The Banu Kinda tribe had gained the strength and numbers to fill that role, so from 425 the Himyarite king Hasan ibn Amr ibn Tubba’ made Hujr Akil al-Murar ibn Amr the first King of Kinda.

At this time, the Ghassanids, Lakhmids and Kindites were all Kahlani Qahtani vassal kingdoms appointed by the Romans, Persians and Himyarites, respectively, to protect their borders and imperial interests from the raids of the then rising threat of the Adnani tribes.

The Kindites had been the most successful in pacifying the Adnani tribes of Central Arabia through alliances and focused on wars with the Lakhmids.

The conversion of the Himyarite kings to Judaism in the late fifth century had led to the conversion to Judaism of the Kindites.

The transition of the power in Yemen to Christian Axumites in 525, when the latter invaded Himyar, appears to have significantly undermined Kindite Judaism, however; the Kindites had gradually declined, their kingdom splitting within three years into several small polities, subsequently destroyed in the 530s and 540s in a series of uprisings of the Adnani tribes against the Kindite kings.

Hujr, the last king of the Banu Kindah, had failed to revive the kingdom ruled by his father and had been assassinated sometime in the 530s.

His grieving son, Imru’ al-Qais ibn Hujr al-Kindi, writes moving poetry and forgoes the pleasures of wine and women until he can take revenge upon his father’s assassins.

Upon completing his mission, al-Qais goes on to enliven the stereotyped genre of Arabic poetry called the “qasidah” (ode) with personal love experiences and richly descriptive detail.

Raised in luxury as a prince, he suffered because he was deprived from ruling after his father’s assassination, which is why Arabs called him al-Malek-al-Delleel or the Shadow King.

(He dies around 544, believed to have been assassinated on the orders of Emperor Justinian, who had sent him a poisoned cloak after al-Qays had an affair with a princess at his court.)

In 540, the Lakhmids destroy all the Kindite settlements in Nejd, forcing the Banu Kindah to move back to the Hadhramawt.

With the Axumites ruling in Western Yemen, the Kindites and most the Arab tribes will soon switch their alliances to the Lakhmids.

Dhu Nuwas, who had been the Jewish Himyarite ruler of Yemen, at this time a rich and fertile land, had in the period around 520 or a bit later launched military operations against the Axumites in Southern Arabia along and their local Arab Christians allies.

The Axumites in Zafar had been killed, their fortresses in the Yemeni highlands destroyed, the coastal regions reconquered, and Najran sacked.

When Najran had fallen in 518 or 523, many members of the Himyarite Christian community had been put to death, evoking great sympathy throughout the Christian regions of the Orient and prompting an Axumite military intervention aided by an imperial fleet.

Abraha, an Ethiopian Christian, had either been one of the commanders or a member of one of the armies led by King Kaleb (Helestheaios) of Axum against Dhü Nuwäs.

Following the suicide of Dhü Nuwäs, Abraha had seized power and established himself as viceroy at Sana'a.

Abraha is said to have repaired the principal irrigation dam at the ancient Sabaean capital of Ma'rib.

A zealous Christian, he calls for a massacre of Jews.

As governor of the territories in Arabia for the Axumite Kingdom, Abraha is an ally of the Romans against the Persian king Khosrau I.

Justinian had offered to make peace with Vitiges, but Belisarius had refused to transmit the message.

The Ostrogoths now offer to support Belisarius as emperor of the West.

In May, Belisarius conquers Mediolanum and …

Flavius Magnus Aurelius Cassiodorus, a Roman scholar, author, and diplomat who held high office under Theodoric the Great and other Ostrogothic kings of Italy, retires from public life around 540.

He establishes two monasteries at Vivarium, his estate in Calabria on the shores of the Ionian Sea.

Here, he pursues scholarly activities, especially writing, and encourages monks to devote their free time to the copying of old religious and secular manuscripts.

The Apulian city of Taranto returns in 540 to the fold of Empire.