Interior East Africa (1108 – 1251 CE): The Zagwe Golden Age and Expanding Great Lakes Polities

Yi Seonggye’s son Yi Gyeong had followed his father to various battlefronts and fought at his side during the latter days of the declining Goryeo Dynasty.

The king’s first wife, who gave birth to six of the king's sons including Yi Gyeong, had died before King Taejo was crowned.

Taejo had gotten two sons by his second wife; he favors his youngest son.

Prime Minister Jeong Dojeon also backs him as the heir apparent, to the great disappointment of the other princes.

In 1398, King Taejo's fifth son, Yi Bangwon, had led a coup staffed by several military officers and killed the queen, her two sons, Prime Minister Jeong, and many of his adherents.

Yi Bangwon, at pains not to be thought of as a usurper, had promoted Yi Gyeong, who is at this point the eldest son, as crown prince.

King Taejo, understandably upset, abdicates in disgust, and Yi Gyeong becomes King Jeongjong in 1399.

The same year, …

…Jeongjong moves the capital back to Kaesong, the old Goryeo capital, where he is believed to have been considerably more comfortable.

Meanwhile, Yi Bangwon, not in the least discouraged by the fact that his elder brother holds the throne, begins plotting to be invested as Royal Prince Successor Brother, the traditional title for brothers appointed as heir-presumptives to the throne when the incumbent has no issue.

However, Yi Bangwon's plans are opposed by Taejo's fourth son Yi Banggan, who also yearns for power.

The tensions between Yi Bangwon's faction and Yi Banggan's camp escalate in 1400 into an all-out conflict that will come to be known as the Second Strife of Princes.

In the aftermath of the struggle, the defeated Yi Banggan is exiled to Tosan, while those who had urged him to battle against Yi Bangwon are executed.

Thoroughly intimidated, King Jeongjong immediately invests Yi Bangwon as heir presumptive and voluntarily abdicates.

This same year, Yi Bangwon finally assumes the throne of Joseon as King Taejong.

The Joseon Dynasty is in 1401 officially admitted to enter into a tributary relationship with the Ming Dynasty.

Meanwhile, the Grand King Former, Taejo, has refused to relinquish the royal seal that signifies the legitimacy of any king's rule.

Uncomfortable at the fact that his father does not recognize him as a de jure ruler because of the family deaths he has caused, Taejong has sent several messengers, among them his childhood friend Bak Sun, to recover the royal seal.

However, Taejo has ordered the assassination of every messenger that comes into the sight of his guards as a sign of his fury at Taejong, who continues to remain unaware of their fates. (This episode is to become known as the Case of the Hamhung Envoys, and the term "Hamhung envoy" is still used to refer to a person who has gone on an assignment from whom there is no reply concerning their whereabouts.)

Taejong, whose father is unwilling to pass over the royal seal he needs for recognition, begins to initiate policies he believe will prove his intelligence and right to rule.

One of his first acts as king had been to abolish the privilege enjoyed by the upper echelons of government and the aristocracy to maintain private armies.

His revoking of such rights to field independent forces has effectively severed their ability to muster large-scale revolts, and has drastically increased the number of men employed in the national military.

As part of a cultural project, a map of the world, the Kangnido (the full Hanja name means "Map of Integrated Lands and Regions of Historical Countries and Capitals"), is created under the supervision of two high Korean officials, and the Confucian scholar Kwon Kun.

It is the second oldest surviving world map from East Asia, after the similar Chinese Da Ming Hun Yi Tu, part of a tradition begun in the 1320s when geographical information about western countries became available via Islamic scholars in the Mongol empire.

It depicts the general form of the Old World, from Africa and Europe in the west to Japan in the east.

Although, overall, it is less geographically accurate than its Chinese cousin, most obviously in the depiction of rivers and small islands, it does feature some improvements (particularly the depictions of Korea and Japan, and a less cramped version of Africa).

Taejong's next act as king had been to revise the existing legislation concerning the taxation of land ownership and the recording of state of subjects.

Although many aristocrats who had benefited from King Taejo's laws redistributing property from the Gwonmun aristocrats to the members of the Sinjin faction have managed to avoid taxation by deliberately hiding land they acquired, King Taejong's re-investigation of land ownership in 1405 puts an end to such practices.

With the discovery of previously hidden land, national income doubles.