…Caracalla retires to Edessa. The Praetorian prefect…

Zhang Lu, who dies not long after surrendering to Cao Cao, is created a marquess.

The Five Pecks of Rice religion is continued by his sons, eventually to evolve under the Tang Dynasty into the Taoist religion known as Zhengyi Dao, or the Way of Complete Orthodoxy.

Cao Pi was born in 187 to Cao Cao and one of his favorite concubines, Lady Bian.

At the time of Cao Pi's birth, Cao Cao was a mid-level officer in the imperial guards in the capital Luoyang, with no hint that he would go on to the great campaigns he eventually carried out after the collapse of the imperial government in 190.

In the period after 190 when Cao Cao was constantly waging war, it is not known where Cao Pi and his mother Lady Bian were, or what their activities were.

The lone reference to Cao Pi during this period was in 204, when he took Yuan Xi's wife Lady Zhen as his wife.

(Lady Zhen gave birth to Cao Pi's eldest son Cao Rui only eight months later—which created murmurs that Cao Rui might have been biologically Yuan Xi's son and not Cao Pi's, although the possibilities appeared farfetched.)

The next immediate reference to Cao Pi's activities was in 211, when he was commissioned to be commander of the imperial guards and deputy prime minister.

This position made him assistant to his father, who was then prime minister and effectively in control of the imperial government.

His older brother Cao Ang had died earlier, and Cao Pi is now the oldest son of Cao Cao.

Futher, his mother Lady Bian is now Cao Cao's wife (after Cao Ang's adoptive mother, Cao Cao's first wife Lady Ding, was deposed), thus making Cao Pi the presumptive heir to Cao Cao.

However, his status as heir is not immediately made legal, and for years there are lingering doubts on whom Cao Cao intends to make heir.

Cao Cao greatly favors Cao Zhi, a younger son of his also by Lady Bian, who is known for his literary talents.

Both Cao Pi and Cao Zhi are talented poets, but Cao Zhi is more highly regarded as a poet and speaker.

By 215, the brothers were in concord on the surface but each had his own set of associates fighting each other under the surface.

Initially, Cao Zhi's party appears to be prevailing, and in 216 they are successful in falsely accusing two officials supporting Cao Pi—Cui Yan and Mao Jie.

Cui is executed, while Mao is deposed.

However, the situation shifts after Cao Cao receives advice from his strategist Jia Xu, who concludes that changing the general rules of succession (primogeniture) would be disruptive—using Yuan Shao and Liu Biao as counterexamples.

Cao Pi is also burnishing his image among the people and creates the sense that Cao Zhi is wasteful and lacking actual talent in governance.

Zhang He, in anticipation of a prolonged war, leads his army to Dangqu in order to relocate the population of Ba to Hanzhong.

Meanwhile, Liu Bei appoints Zhang Fei as Administrator of Baxi and orders him to take over the region.

Zhang Fei and Zhang He face each other for fifty days, which concludes with a victory for the former, following a surprise attack on the latter.

Narrowly escaping, Zhang He retreats to Nanzheng on foot, and the Ba region becomes part of Liu Bei's territory.

Artabanus IV of Parthia had rebelled against his brother Vologases VI of Parthia soon after the latter's succession to the throne around 212 and gained control over a greater part of the empire.

Vologases VI maintains himself in a part of Babylonia.

The Roman emperor Caracalla, wishing to make use of this civil war for a conquest of the East in imitation of his idol, Alexander the Great, marches into Mesopotamia under the pretext of marrying one of Artabanus' daughters.

Caracalla, according to the historian Herodian, tricked the Parthians in 216  into believing that he accepted a marriage and peace proposal, but then had the bride and guests slaughtered after the wedding celebrations.

The thereafter ongoing conflict and skirmishes become known as the Parthian war of Caracalla.

After deposing the kings of Osroene and Armenia to make them Roman provinces once more, he crosses the Tigris, destroys the towns, and spoils the tombs of Arbela, but when Artabanus advances at the head of an army, …

The expulsion of foreigners from Alexandria causes Ambrose to take refuge in Caesarea, where he seems to have made his permanent home; and Origen leaves Egypt, apparently going with Ambrose to Caesarea, where he spends some time.

Here, in conformity with local usage based on Jewish custom, Origen, though not ordained, preaches and interprets the Scriptures at the request of the bishops Alexander of Jerusalem and Theoctistus of Caesarea.

When, however, the confusion in Alexandria subsides, Demetrius, bishop of Alexandria, who views this activity as a breach of discipline, orders him, probably in about 216, to return to Alexandria.

Seeking to secure his own legacy, Caracalla also commissions one of Rome's last major architectural achievements, the colossal and richly decorated Baths of Caracalla, the largest public baths ever built in ancient Rome.

Reportedly built in Rome between 212 and 216, the builders would have had to install over 2,000 tons of material every day for six years in order to complete it in this time period.

Chris Scarre provides a slightly longer construction period 211-217 CE. ("Seventy Wonders of the Ancient World" edited by Chris Scarre [1999], p. 178).

Records show that the idea for the baths had been drawn drawn up by Septimius Severus, and merely completed or opened in the lifetime of Caracalla.

This would allow for a longer construction time frame.

The main room of the baths is larger than St. Peter's Basilica, and can easily accommodate over two thousand Roman citizens at one time.

The bath house opens in 216, complete with libraries, private rooms and outdoor tracks.

Internally it is lavishly decorated with gold-trimmed marble floors, columns, mosaics and colossal statuary.

Colossal cisterns rest beneath the stadium against the rear walls.

Opposite, across the acres of gardens, is the enormous central building.

Planned in strict symmetry, the four main halls, on a central axis, are the circular caldarium (hot bath), topped with a dome more than one hundred feet (thirty-three meters) high; the tepidarium (warm bath); the huge triple-vaulted frigidarium (cold bath), which is two hundred feet (sixty-six meters) long; and the even bigger natatio (swimming pool, probably open to the sky).

Marble revetments, mosaic floors, and decorative statuary ornament the awesome concrete structure.

Cao Cao, who is by this point Prince of Wei, finally declares Cao Pi as his crown prince in 217.

He will remain as such until his father's death in 220.

Fa Zheng, in 217, points out the strategic necessities of seizing Hanzhong and advises Liu Bei to drive Cao Cao's force out of the area.

Liu Bei sends Zhang Fei, Ma Chao, and several subordinate generals to Wudu, while he assembles an army and advances to Yangping Pass.

Zhang Fei is forced to retreat after his aides Wu Lan and Lei Tong are defeated and killed by Cao Cao's forces.

Liu Bei, engaging Xiahou Yuan at Yangping Pass, tries to cut the enemy's supply route by sending his general Chen Shi to Mamingge, but is routed by Xiahou's subordinate, Xu Huang.

Liu Bei then presses on Zhang He at Guangshi but fails to achieve any success; at the same time, Xiahou Yuan and Zhang He are not able to hinder Liu Bei from mobilizing forces around the area.

The war turns into a stalemate, and Cao Cao decides to gather an army in Chang'an to fight Liu Bei.

Macrinus is confirmed in his new role by the Senate despite his equestrian background.

According to S.N.

Miller, this may have been due to both his background as an accomplished jurist and his deferential treatment of the senatorial class.

(Miller, S.N., "The Army and the Imperial House," The Cambridge Ancient History, Volume XII: The Imperial Crisis and Recovery (A.D. 193–324), S.A. Cook et al.

eds, Cambridge University Press, 1965, pp 50–2.)

He finds it necessary, however, to replace several provincial governors with men of his own choosing.

Caracalla's mother Julia Domna is initially left in peace, but when she starts to conspire with the military he orders her to leave Antioch.

Being at this time in an advanced stage of breast cancer (Cassius Dio) she chooses instead to starve herself to death.

In urgent matters of foreign policy, Macrinus displays a tendency towards conciliation and a reluctance to engage in military conflict.

He averts trouble in the province of Dacia by returning hostages that had been held by Caracalla, and he ends troubles in Armenia by granting that country's throne to Tiridates, whose father had also been imprisoned under Caracalla.

Less easily managed is the problem of Mesopotamia, which has been invaded by the Parthians in the wake of Caracalla's demise.

Monuments are built to revere Macrinus at a high point of his popularity.

The grand tetrastyle Capitoline Temple in Volubilis is erected to honor him in 217.

Meeting the Parthians in battle during the summer of this year, Macrinus achieves a costly draw near the town of Nisibis and as a result is forced to enter negotiations through which Rome is obliged to pay the enormous indemnity of two hundred million sesterces to the Parthian ruler Artabanus IV in return for peace.

However, Macrinus displays some financial farsightedness when he revalues the Roman currency.

He increases the silver purity of the denarius from 51.5% to 58%—the actual silver weight increasing from 1.66 grams to 1.82 grams.

Nevertheless, Macrinus' reluctance to engage in warfare, and his failure to gain victory over even a historically inferior enemy such as the Parthians causes considerable resentment among the soldiers.

This is compounded by him curtailing the privileges they had enjoyed under Caracalla and the introduction of a pay system by which recruits receive less than veterans.

After only a short while, the legions are searching for a rival emperor.

His popularity also suffered in Rome.

Not only has the new emperor failed to visit the city after taking power but a late-summer thunderstorm causes widespread fires and flooding.

Macrinus' appointee as urban prefect proves unable to repair the damage to the satisfaction of the populace and has to be replaced.