You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Chinese_characters

Context:
After Kim Jong Il, the second ruler of North Korea, died in December 2011, Kim Jong Un stepped up and began mandating the use of Hanja as a source of definition for the Korean language. Currently, it is said that North Korea teaches around 3,000 Hanja characters to North Korean students, and in some cases, the characters appear within advertisements and newspapers. However, it is also said that the authorities implore students not to use the characters in public. Due to North Korea's strict isolationism, accurate reports about hanja use in North Korea are hard to obtain.

Question:
Who began moderating the use of Hanja?

Kim Jong Un