II. Historical Setting, Authorship, And Date
The armies of Assyria swept into Palestine in 734 B.C., bringing both the northern kingdom of Israel and the kingdom of Judah under their control. Israel was wiped out in 722 or 721 b.c. Judah retained its identity but not its independence. The book claims to contain the vision of Nahum, and there has been little reason to deny him its authorship.
The date of Nahum's prophecy and its authorship would be just before the fall of Nineveh in 612 b.c.