The Deuteronomist, abbreviated as either Dtr or simply D, may refer either to the source document underlying the core chapters (12–26) of the Book of Deuteronomy, or to the broader "school" that produced all of Deuteronomy as well as the Deuteronomistic history of Joshua, Judges, Samuel, Kings, and also the Book of Jeremiah. The adjectives "Deuteronomic" and "Deuteronomistic" are sometimes used interchangeably; if they are distinguished, then the first refers to the core of Deuteronomy and the second to all of Deuteronomy and the history. The Deuteronomist is one of the sources identified through source criticism as underlying much of the Hebrew Bible. Among source-critical scholars, it is generally agreed that Deuteronomy and the Deuteronomistic history originated independently of the books of Genesis, Exodus, Leviticus and Numbers (the first four books of the Torah, sometimes called the "Tetrateuch", whose sources are the Priestly source and the Jahwist), and the history of the Books of Chronicles; most scholars trace all or most of it to the Babylonian exile (6th century BCE), and associate it with editorial reworking of both the Tetrateuch and Jeremiah. Background Since the mid-20th century, scholars have imagined the Deuteronomists as country Levites (a junior order of priests), or as prophets in the tradition of the northern Kingdom of Israel, or as sages and scribes at the royal court. Recent scholarship has interpreted the book as involving all these groups, and the origin and growth of Deuteronomism is usually described in the following terms: Following the destruction of Israel (the northern kingdom) by Assyria in 721 BCE, refugees came south to Judah, bringing with them traditions, notably the concept of Yahweh as the only God who should be served, which had not previously been known. Among those influenced by these new ideas were the landowning aristocrats (called "people of the land" in the Bible) who provided the administrative elite in Jerusalem. In 640 BCE there was a crisis in Judah when king Amon was murdered. The aristocrats suppressed the attempted coup, putting the ringleaders to death and placing Amon's eight-year-old son, Josiah, on the throne. Judah at this time was a vassal of Assyria, but Assyria now began a rapid and unexpected decline in power, leading to a resurgence of nationalism in Jerusalem. In 622 BCE Josiah launched his reform program, based on an early form of Deuteronomy 5–26, framed as a covenant (treaty) between Judah and Yahweh