@Riu Essentially Yi Seong-Gye was a general that performed a successful coup and large part of that success was due to the actions of Yi Bang-won, his fifth son. Seong-Gye eventually became King Taejon ushering in the Joseon Dynasty. The issue, without going into much detail, stemmed from the matter of succession. Bang-won believed because of what he did during the coup, he had earned the right to be the next king, but his father opted for his youngest son, Bang-won's half brother, the eighth prince who was crowned heir apparent. Obviously, this did not sit well with the first 6, so essentially Bang-won got his younger half brother's, the 7th and 8th prince, killed in a coup alongside a key advisor who supported the succession of the 8th prince. This event was called "Strife of the princes." Again I'm going to leave out some detail here but essentially in the end Seong-gye abdicated and Bang-won becomes the third king after his older brother eventually abdicated the throne to him.