Zhu Zhanji was born in 1398. He was the son of Zhu Gaozhi, and grandson of Zhu Di, the Emperor Chengzu (Yongle Emperor), the first year of his reign.

Yongle was the force behind the strengthening of the Chinese navy and instituted major reforms in the empire. It was in 1421 that Yongle sent the famous fleet led by Zheng He, that was said to have discovered the new world.

Yongle died in 1424, and his son, who became the Emperor Ren (Hongze Emperor), only reigned a year before he died, but long enough to allow the fleet to fall into lethargy.

Zhu Zhanji was then proclaimed the Emperor Xuan (or XuanZong), the Xuande Emperor in 1426. Xuande reformed management of the empire, and reinforced the great wall. He seemed to be more focused on strenghtening the interior rather than the fleet, and although the final voyage took place prior to Xuande's death, the deconstruction of the fleet had already begun.

Xuande died in 1435, to be succeeded by his son, Zhu Qizhen, or the Zhengtong Emperor.

I found this on the net, at http://www.ac.wwu.edu/~kaplan/H370/mp31.pdf:

a. Domestic expansion The Yongle Emperor died in 1424. His son succeeded him on the throne, but died within a year and a half, and was followed by the Yongle Emperor’s grandson, the Xuande Emperor. He, however, reigned for only a decade. The Xuande Emperor was not a chip off the old Yongle block except physically. Like his grandfather, he was a big, beefy man with big jowls and a bigger bottom to his head than a top (at least judging from his portrait in the palace collection), but was mild in manner and humane.

Unlike his grandfather, his reputation is not at all that of a barbarian. He instead seems to have been a throwback in temperament to his great-uncle, the late Jianwen Emperor, except that he was a bit of a womanizer. He was also a very fine painter, one of the best animal figure painters and still life painters since the Emperor Huizong at the end of Northern Song.

Xuande also encouraged the growth of the porcelain industry at Jingdezhen, which during his reign began to come fully into its own.

This emphasis on things civil is not what you might expect from some chip off the block of the Yongle Emperor.

The Xuande Emperor did have to get through some tough times. Right after he took the throne in 1426, his uncle, a younger son of the Yongle Emperor, rebelled, just as the Yongle Emperor himself had done in 1402. However, history did not fully repeat itself, perhaps because there was no extra uncertainty created by this being a first succession.

This time around the nice guy won. Partly thanks to the loyalty of the meritocracy, the uncle’s rebellion was put down. Even the military meritocracy had learned the uses of loyalty by then. Both civilian and military men of merit realized they were much better off with this humane, civilian- minded emperor than they would have been with another Mongol-style imperial bruiser.

In many ways, therefore, the Xuande reign was thought of by the meritocracy at the time and since as a kind of restoration, a going back to the right course exemplified by the abortive Jianwen reign of 1398 to 1402. Xuande’s death after just a decade on the throne came as a shock to both court and people, and was much regretted then and since. Some Chinese historians even date the beginning of Ming’s decline to as early as 1436, the year of Xuande’s death.

b. Foreign retrenchment. But of course by the 1420s the meritocrats already possessed the advantages that the Yongle Emperor had granted to them. They were already permanently ensconced in Peking, the northern capital, close to the Great Wall, a city with its back (metaphorically speaking) to the sea. Nanking, within convenient commuting distance of the great ports at the mouth of the Yangzi, remained only as the secondary capital.

This was much as was the case under Tang and Han and Zhou, when the main capital was in the west at Xi’an to guard the land frontiers, and the secondary capital was to the east at Loyang, closer to the main land trade routes. Also, as earlier, separate central administrations were maintained at each capital, thereby doubling the opportunities for the meritocrats to compete for high ranking jobs.

The meritocracy preferred to use this elaborate administration more for domestic than foreign purposes, the better to feather their nests and deny power as plutocrats to rich seagoing merchants. Fortunately for the men of merit, but under circumstances that ultimately involved greater hardships for ordinary Chinese, from the Xuande reign on, Ming was distracted from overseas adventures.

The second quarter of the 15th century seems to have been one of those still little understood cyclical periods of bad weather In Europe too this “little ice age” wrecked havoc with agriculture. The Ming government had to carry out extensive relief measures, particularly in North China. The need to move grain for relief purposes and to provide employment for displaced farmers led the authorities to hasten to restore the Grand Canal. The authorities preferred to use Zheng He’s sailors as barge-pullers on that canal from the end of the 1420s through the 1430s rather than resume the eunuch’s voyages. Yongle’s Vietnam invasion ended after his death with the Chinese declaring they had won, and then pulling out, much as the U.S. was advised to do at the end of the 1960s. The Chinese did not even get the Vietnamese to accept full tributary status, so this was by no means a victory, even nominally.

The Xuande Emperor was still using eunuchs for political purposes, but more cautiously than had Yongle. Most eunuchs were still, as Zheng He had been, Muslims. Zheng, who hailed from Yunnan, belonged to a family of foreign extraction who had accompanied the Mongols during Kubilai’s campaigns into Yunnan.

However, the new fashion was to use Koreans for eunuchs. Koreans were also foreigners, but in Chinese eyes seemed a more domesticated kind of foreigner. Eventually, by late Ming, most eunuchs were Chinese and even came from the same place, a county near Peking which specialized in exporting eunuchs to the court.

Over time, eunuchs began to tilt away from their earlier overseas merchant connection and toward imitation of the meritocrats. During the Xuande reign a school for eunuchs was established at court. It was called the Neishutang, and provided a standard meritocratic education for the eunuchs.

With this step the eunuchs began to evolve in the direction that would ultimately make them the purest form of meritocrat, with no family connections at all to rival their allegiance to the throne, at least in principle, but with enough education to function as sophisticated meritocrats from their secure base in the Inner Court.

Concern over the Mongols became ever greater in the course of the Xuande reign. This was one reason why the Xuande Emperor was so unenthusiastic about renewing Yongle’s voyages of exploration overseas. The next reign, the Zhengtong reign, 1436-49, ended in disaster when the Zhengtong Emperor was captured by the Mongols while leading an expedition against them in the southern part of Inner Mongolia.

However, this political disaster ended in a kind of low comedy. The new Jingtai Emperor, r. 1450-1456, was not particularly eager to have his predecessor come back because he was rather enjoying being emperor himself, and could not be sure if the old ruler would be magnanimous if restored to the throne or would treat him as a usurper and put an end to him altogether.

Based on Xtreemli's information, it would seem that our POD take sometime earlier during Xuande's reign, prior to the deconstruction of the fleet and the seventh voyage, between 1425-1430