Detailed Instructions: This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.
Q: Passage: Following Kammu's death in 806 and a succession struggle among his sons, two new offices were established in an effort to adjust the Taika-Taiho administrative structure. Through the new Emperor's Private Office, the emperor could issue administrative edicts more directly and with more self-assurance than before. The new Metropolitan Police Board replaced the largely ceremonial imperial guard units. While these two offices strengthened the emperor's position temporarily, soon they and other Chinese-style structures were bypassed in the developing state. In 838 the end of the imperial-sanctioned missions to Tang China, which had begun in 630, marked the effective end of Chinese influence. Tang China was in a state of decline, and Chinese Buddhists were severely persecuted, undermining Japanese respect for Chinese institutions. Japan began to turn inward.
A:
who's sons died in 806?