Samjeondo, which required Injo's first and second son to be taken to China as captives. Joseon then became a tributary state to the Qing dynasty, and the Qing went on to conquer the Central Plain in 1644. Death of the Crown Prince After Qing conquered Beijing in 1644, the two princes returned to Korea. Injo's first son, Crown Prince Sohyeon, brought many new products from the western world, including Christianity, and urged Injo for reform. However, the conservative Injo would not accept the opinion; and persecuted the Crown Prince for attempting to bring in foreign Catholicism and Western science into Korea. The Crown Prince was mysteriously found dead in the King's room, bleeding severely from the head. Legends say that Injo killed his own son with an ink slab that Sohyeon brought from China; however, some historians suggest he was poisoned by the fact that he had black spots all over his body after his death and that his body decomposed rapidly. Many, including his wife, tried to uncover what happened but Injo ordered immediate burial and greatly reduced the grandeur of the practice of Crown Prince's funeral. King Injo even shortened the funeral period for his son. King Injo appointed Grand Prince Bongrim as new Crown Prince (who later became King Hyojong) rather than Prince Sohyeon's oldest son, Prince Gyeongseon. Soon after, Injo ordered the exile of Prince Sohyeon's three sons to Jeju Island (from which only the youngest son, Prince Gyeongan, returned to the mainland alive) and the execution of Sohyeon's wife, Crown Princess Minhoe, for treason. Legacy Today, Injo is mostly regarded as a weak, indecisive and unstable ruler; for he caused the Yi Gwal Rebellion, two wars with the Qing dynasty, and a devastation of the economy. He is often compared to his predecessor, Gwanghaegun, who was dethroned, while Injo had almost no achievements during his reign and was still given a temple name. Blamed for not taking care of his kingdom, many people regard King Injo as a model for politicians not to follow; yet, he is credited for reforming the military and expanding the defense of the nation to prepare for war, since the nation had several military conflicts from 1592 to 1636. Injo died in 1649. His tomb is located in Paju, Gyeonggi Province. Family Father: Wonjong of Joseon (2 August 1580 – 29 December 1619) (조선 원종) Grandfather: King Seonjo of Joseon