From Search the Scriptures, by Alan M. Stibbs:
Jonah is mentioned in 2 Ki. 14:25 as having predicted the victories of Jeroboam II by which the borders of the kingdom of Israel were greatly enlarged. If Jonah prophesied at the beginning of Jeroboam’s reign, he would precede Amos by about twenty years only. At that time Assyria was already a great power, and had begun to reach out westwards: in fact, Jeroboam’s victories were partly due to Assyrian raids upon Damascus and neighbouring states, which weakened these kingdoms. It would seem that Jonah was afraid of Assyria, whose cruelties were well known, and whose power was dreaded.
To this man came the commission to go to Nineveh and cry against it. One might have thought that such a commission would not be unwelcome, but to Jonah it was so hateful that he resolved rather to resign his prophetic office than obey it. The book is the story of what happened. It is one of the most remarkable books in the Bible, and rich in spiritual teaching.