Israel had already deviated from faithfulness, but here, she formally rejects God as her Ruler, taking a major step toward being exactly like all the nations around her. This occurred between 1100 and 1000 BC or roughly 350 years after the original making of the covenant. Except for brief periods when Israel had a judge or king who did right in the eyes of God, the spiritual harlotry continued unabated until God formally divorced her, sending Israel and Judah into captivity.
We frequently gloss over the truly important part of this as we read through it. It is clear from Genesis 17:6 and Deuteronomy 17:14-20 that God anticipated Israel having a king or judge. The title is of little importance. Having a king was not the real issue because God had already planned for Israel to have a king. Every organization must have a leader, so God lays down instructions as to how the leader should conduct himself in office. They are designed to ensure that the king does not elevate himself above the people and rule as a despot. Instead, he is to be thoroughly familiar with and guided by the attitudes and laws of God. He must comprehensively know that his own nature is just like those he serves and be humbled.
However, the key to understanding the significance of Israel's demand in I Samuel 8 is that she desires a king just like the other nations. Spiritually, this demand confirms Israel's whorish behavior, and thus God tells Samuel to describe the national effects of her demand. On Israel's part, it is a complete rejection of her marriage vows; she wants her Benefactor and Husband—God—to have no say in her life, declaring herself free of Him and to be completely and totally a nation of this world, no longer the type of God's Kingdom on earth.
The issue between God and man is simply a matter of government—of sovereignty and providence. This appears as early as Genesis 3 when Adam and Eve reject God's rule over them. Once God reveals Himself through His calling, the issue of government comes to the fore. This is what we confront in decision-making. As the Bible has recorded in great detail, mankind has shown that it wants to retain this authority to itself. Yet, the naked truth is we cannot retain sovereignty to ourselves and still have what God is offering, entrance into the spiritual Kingdom of God. We cannot have it both ways. We will be submissive either to God's will or to our own fickle drives. Many of us do not get it!