Final answer:
Saul was indeed from the tribe of Benjamin, and his kingship marked the beginning of the united monarchy period.
Step-by-step explanation:
It is true that Saul was from the tribe of Benjamin and not Judah. Saul became the first king of Israel around 1020 BCE as the Hebrews organized themselves into a kingdom to defend against Philistine oppression.
While there was no specific rule stating only a member of the tribe of Judah could become king, the subsequent king, David, was indeed from Judah, establishing a precedent that later became significant in Jewish and Christian traditions as it was from this lineage that the Messianic expectations arose.
The early Hebrew kings, including Saul, David, and Solomon, ruled during what historians call the united monarchy period.
Archaeological evidence, such as the Tel Dan stele, supports the historical existence of the house of David, though there remains debate about the biblical accounts of these figures.
After Solomon's reign, the kingdom divided into Israel in the north and Judah in the south, with Jerusalem remaining the capital of Judah.