As Moggallana returned to his capital in Anuradhapura and seemed, on the face of it, to be restoring life to whatever had passed for normal before his brother Kassapa had murdered their father, it might have been hoped that national life would steady. But steadiness was not what lay ahead for either Sri Lanka or the rest of the Moriyan kings still to come. By the end of Moggallana’s reign, it would look as if an infernal inheritance had instead settled across the land.

For Moggallana’s route to power lay through the implacable and rough power politics of the Indian Ocean Trading Zone. It was not just the turncoat General Migara who had propelled him to power, but a mercenary army, the clutches of which would enfold the entire kingdom to a greater or lesser extent until the very end of the Moriyan dynasty itself.

The old story told of these times is of a Tamil mercenary army coming to Moggallana’s aid and then departing again, job done. But remarkable research by a new generation of historians, most notably Ranjan Mendis, has shown that this is far from the truth.

The real story begins in Persia, 3800 kilometres away - and with the ambitions of the Persian king of kings, Khosrow I ("the Immortal Soul"), to expand his empire in all directions and drive a cleaver through the Byzantine Roman end of the Maritime Silk Road trading empire, which the Emperors of Constantinople managed through their Ethiopian and Yemeni allies. Shutting off the Romans from any meaningful access to India and Sri Lanka via the Red Sea would hand Khosrow the world's most lucrative commercial monopoly.

It was superpower politics, an ancient world version of it, just as life-changing as that witnessed today between America, Russia, China, and India. Khosrow’s first step was to capture Yemen, which had earlier fallen to the Ethiopians on the request of the Constantinople Emperor Justinian to, as Procopius of Caesarea put it, “ sever Persians’ maritime links with India.” But securing the Maritime Indian Ocean trading route even further east than Yemen was an irresistible cherry in Persian ambitions. It would place it well beyond the reach of the Roman emperors once and for all.

Plots were hatched. Messages were passed to Moggallana, who was then in long-term exile somewhere in South India, with the help of General Migara, a clandestine network of Persian Christian merchants living in Anuradhapura. By letter, and possibly even by his presence before the Persian king, Moggallana wove his way into the plan to ensure Sri Lanka became a safe house for Persian trade. He, as the new ruler, would be its guarantor – a Trojan horse as much as a replacement king.

A fleet of Persian ships carrying an elite Savaran cavalry contingent sailed to Sri Lanka, perhaps even under the direct command of Moggallana himself. They may have even taken with them the terrible new weapon used by the Persians just a few years earlier against Constantinople – petroleum and naphtha. They landed somewhere on the western seaboard of the island – possibly Chilaw- before marching inland to Kurunegala, so smartly circumnavigating both Anuradhapura and Sigiriya and catching both power centres off balance. Mistaking to the last that the presence of General Migara by his side meant that he was covered, Kashyapa opted for suicide rather than capture when the general flipped his forces.

Writing a few centuries later, the historian Al-Tabari notes of the moment: “the king sent one of his commanders with a numerous army against Serendib, the land of precious stones, in the land of India. The commander attacked the king, killed him, and seized control of it, sending back from here to Kisa abundant wealth and many jewels.” Clearly, the Persians wasted no time in ransacking the sensational riches of Sigiriya. Later Persian commentators record that the flow of bounty never really ceased. It continued for years to come and, in addition to items such as horses, jewels, and natural resources, elephants, teak, and pearl divers. It was less the gifts of one grateful king to another, and more tribute paid by a vassal to his master.

Unlike Kashyapa, who referred to himself as Maharaja or Great King, the inscriptions so far discovered for his brother Moggallana, and even Moggallana’s heir, merely refer to them as Rajas. Raja is most certainly a title used by lesser kings – kings beholden to other kings, not least Persian kings of kings. Studies of ancient texts by Professor Paranavitana suggest that the Anuradhapuran monks welcomed him as an imperial representative of the Persian king, not as a Sri Lankan king in his own right. Little good it did them, for the new king sided with the new money and the newer version of religion in the old city and did nothing to stop his merchants from unleashing so unremittingly barbaric a bout of bloodshed against often quite blameless people that the new king gained another title: “Rakshasa” – monster.

Persian imports flooded into the country – there is even evidence of Persian wine jars found in small villages near Dambulla, not known then, or now, for its predilection for fine wines. Excavations dating back to these times have revealed an abundance of Persian coinage and a Persian Nestorian cross, whilst testifying to the presence of scores of Persian ships docking in Sri Lankan ports. But of Roman artefacts found in plenty before this time, archaeologists today have unearthed nothing dating to this transformative period before the country pivoted towards Persia.

Moggallana is also known to have invested in a new navy to patrol the sea coasts, possibly tasked with deterring Roman ships, including those sent by Roman allies. Sri Lankan embassies sent to the Chinese emperor, representative at the time of Dhatusena and Kasyapa, abruptly ended and recommenced only in the 7th century as the Moriyan dynasty neared its end, a time that coincided with the collapse of the Persian empire itself when the king of kings fell to the Arab Caliphate in 654 CE.

Little is known of how Moggallana's reign went following the coup that brought him to power. He is presented in history books on the island today as a strong, capable, and respected king who busied himself with monastery and temple improvements – and not as a Persian vassal. His monster status is also conveniently overlooked. The reality must have been much more complicated and nuanced. Keeping the Persian paymasters happy would have been a most consuming task – ensuring they reaped the commercial rewards that brought them to him in the first place, and keeping them in check as best he could, despite their random attacks on his subjects. No less all-consuming would have been simply maintaining the balance of power in Anuradhapura among competing versions of Buddhism, insurgent Christians, Theravada Buddhists, and merchants merely out to make lots of money.

Moggallana would certainly have welcomed a wonderful piece of serendipity when the Kesha Dhatu, the Hair Relic of Lord Buddha, found its way into his kingdom, brought there by a monk he had befriended whilst in exile in India – Silakala Ambasamanera, a Lambakarna ally. The relic was given the grandest of all receptions, carried in a great procession and enshrined in a crystal box placed in a specially built temple. Silakala was said to have been appointed its guardian, a task he took so seriously that he forsook his monkish status and became the king's sword-bearer (Asiggahasilakala) instead. This change of career would haunt the Moriyan kings, for Silakala Ambasamanera proved so adept at warfare that he would later seize the throne for himself.

Moggallana was succeeded in 515 by his son Kumara Dhatusena. It was a shockingly aimable succession. The new king described himself in the only inscriptio...