AT ABOUT THE TIME the Roman armies were burning Carthage during the Third Punic War, Chinese legions were extending the Han empire's boundaries west across the Tarim basin to Sogdiana, east to the Korean peninsula, and south into Vietnam. By the waning years of the second century A.D., when pestilence ravaged Marcus Aurelius' forces, the Han dynasty was also in decline. The imperial court was riven by deadly struggles between nobles and eunuchs in which thousands were purged. Outside the royal capital of Loyang, Taoist prophets raised peasant armies that took over entire provinces. Local magnates entrenched themselves in guarded redoubts, or took thieir menat-arms and joined powerful warlords. From the north came the barbarian Hsiung-nu -- whom the Romans knew as Huns -- to pillage Loyang in 311 A.D., slaughtering 30,000 of its citizens. While many Chinese fled south to the Yangtze Valley where six successive dynasties were founded between 222 and 589 in Chien-K'ang (modern Nanking), northern China was occupied by Turkish, Mongolian and Tibetan peoples who in their turn established 16 separate kingdoms. Divided north and south, east and west, the Chinese empire seemed, like the Roman empire after its capital was sacked by the Goths in 410, destined to fission into feudal states.

For nearly four centuries after the fall of Han, China did remain divided into two or more rival states, and a military aristocracy exercised local rule. But late in the sixth century, the Chinese middle ages took a course of their own. In 581 the Duke o Sui, a noble of mixed Chinese and Turko-Mongol blood serving the Northern Chou state, slew his ruler along with 58 royal relatives, and named himself Emperor Wen-ti of the Sui dynasty. Seven years later his armies decisively defeated the forces of the Ch'en state at Chienk'ang, which was ordered razed, and in 589 south China was forcibly brought under northern rule. At the same time Wen-ti restored the formal structure of Han government, established a civil service examination system, attacked hereditary privilege, and abolished the local commanderies occupied by the military aristocracy. After Wen-ti's death in 604, his son, ruling as Yang-ti, went on to unify the empire economically by lengthening the Grand Canal, and continued to strengthen it militarily by extending the Great Wall. Once again the power of imperial Cina was extended over the Huns, northern Vietnam, and the Turkish Khanates of central Asia. And once again, tribute missions arrived at the heart of the empire, a capital later known as Ch'ang-an ("perpetual peace"), and with two million people living inside a 30-mile square of massive raised walls, the world's greatest medieval city.

The Sui restoration of imperial bureaucratic rule meant that China's later historical development was to be radically different from the feudal pattern which characterized Carolingian Europe. Whereas Charlemagne was only a nominal Roman emperor after his papal coronation in 800, actually garnering support by rewarding his folowers with enfeoffment and grants of land, the two Sui relers genuinely established a centralized Chinese empire like tht of the Han. The institutions which they founded would survive their own brief rule from 581 to 617, and would in turn enable the succeeding T'ang (618-906) and Sung (960-1126) dynasties to crush feudal privileges altogether and create the strongest state of premodern times.

It was the staggering accomplishment of imperial reunification, therefore, that most attracted the later Arthur Wright, professor of history at Yale University, to study the "momentous innovations" of Sui rule. The result of that study is an elegantly writen book, The Sui Dynasty , which has now been posthumously published with the help of Professor Wright's student, Dr. Robert Somers. In its opening pages Wright suggests that if the Sui reunification had failed, then China might well have been forever split into separate states with their own particular "prides and chauvinisms." To Wright, the Sui period was thus "one of those times of decision... in which a civilization is given a distinctive shape, when -- as in this case -- a unity of culture and polity is reestablished as the norm." But that observation in turn raises a compelling question and one to which The Sui Dynasty again and again returns. Given the centuries of division which preceded them, how after all did the two Sui rulers manage to put the empire together again?

Wright's own answer is that of an intellectual historian. Military might and economic strength were alone insufficient. The unification had to depend upon a new "cultural hegemony" exercised by the Sui emperors. This hegemony, which also legitimized their rule, was derived from two sources. The first was traditional Chinese culture: the common classical language, Han political theory, and Confucian ethical principles -- all of which were used by Wen-ti to assert "an ecumenical moral order" and thus draw the empire unto himself. The second source of hegemony was Buddhism, which had come from India during the Han period and which had spread throughout China during the age of division. By reviving the Mahayana Buddhist orders, which were all centered by the emperor upon a single huge temple complex that occupied an entire ward of his capital, Wen-ti gained the support of millions of believers. And by sending Buddhist missionaries to other parts of China to build pagodas to house holy relics of the Buddha, the emperor also presented the Chinese with a new image of kingship, modeled explicitly upon the great Buddhist emperor of India, Asoka, who by ordering the sun to stand still completed 84,000 reliquaries in a single day.

Wen-ti's use of Buddhism was not just opportunistic. Professor Wright's portrait of the first Sui emperor depicts a man of pathological temperament who would first break into homicidal rages, killing those who displeased him with his own hands, and then later suffer the deepest remorse for having murdered so rashly. Macbeth-like, he was haunted by the ghost of the previous emperor he had slain, and so turned to Buddhism to exorcise the phantoms around him. Indeed, as his reign wore on, he turned so far in the direction of Buddhist piety that he abandoned Confucianism altogether. By the time of his death all of the local Confucian schools had been shut, and there was only one imperial college still open with a mere 70 students in attendance.

His son and successor, Sui Yang-ti, was also a devout Buddhist, having taken lay vows before Chih-i, the founder of the famed Tien-t'ai sect. But as the last ruler of the Sui dynasty, Yang-ti has been conventionally portrayed solely as a sadistic and licentious tyrant. Wright's book destroys this stereotype and presents a much more believable figure: an ambitious and harsh despot, to be sure, but a man of refinement and learning as well. Before he became emperor, Yang-ti served as viceroy of Chiang-tu (Yang-chou), where he immersed himself in the literary culture of the southland. He married a high-born southern lady, grew fluent in the Wu dialect of the lower Yangtze, and learned to write classical poetry of his own:

"Amber wine and pale lees, we drink the drifting clouds,

Of long sleeves and clear song, a land of pleasure and delight."

Once emperor, Yang-ti pursued a different cultural strategy than his father. He restored a balance between Buddhism and Confucianism on the one hand, and on the other, he tried to convince the nobility of the south that northerners could share the same civilized literary heritage.

The reign of Yang-ti reached its pinnacle in 609. Thereafter political and social conditions deteriorated. As the emperor traveled constantly between his thre capitals, he came more and more to rely upon a small circle of confidential advisers and secret policemen. Plots, real and imagined, were met with tens of thousnds of executions. In the meantime, vast public works, like the enlargement of the Great Wall and extension of the Grand Ganal, required millions of laborers who were conscripted from the peasantry. Even women, who were not usually liable for corvee, were drafted for these onerous projects. Yet as rebellions began to break out with steady and predictable regularity, Yang-ti obstinately pursued a crusade of his own against the north Korean kingdom of Koguryo, whose king had refused to acknowledge the Sui emperorhs suzerainty. One after another, three costly campaigns were mounted against Koguryo between 612 and 614. Despite repeated failures to force submissions, Yang-ti was preparing to send yet a fourth when he was finally forced to turn his attention back to rebellion on a dozen fronts in China.

Sui Yang-ti was to rule for another three years before being murdered in his bathhouse by a descendant of the same royal family that his father had nearly exterminated. Yang-ti's death finally dispelled wht Robert Somers has described in a coda to The Sui Dynasty as the "lethal atmosphere of fear and hatred" surrounding the two unifiers, father and son. The Sui dynasty thus passed into history, but the imperial unity it had brought back to China remained a vital legacy for the glorious T'ang and Sung dynasties yet to come.