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Why did Syria and Israel threaten Judah during the Syro-Ephraimitic War?

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The prophet Isaiah — Isaiah Miniature of Isaiah, manuscript illumination from *The Siegburg Lectionary*, 12th century.

During the Syro-Ephraimitic War (734–732 BCE), the kingdoms of Syria, led by King Rezin, and Israel, led by King Pekah, invaded Judah to force its king, Ahaz, into a military alliance against the expanding Assyrian Empire.12

At the time, the Assyrian state was a powerful and aggressive force consolidating control over the region. Syria and Israel sought to strengthen their own defensive position by compelling Judah to join their coalition against this common threat.1

The prophet Isaiah famously advised King Ahaz against joining this alliance, urging him instead to place his trust in Yahweh. Ahaz ultimately rejected this counsel and appealed to the Assyrian king, Tiglath-pileser III, for aid. Assyria subsequently defeated the northern invaders, but the decision left Judah as an Assyrian vassal, burdened by heavy tribute and the introduction of foreign religious practices into the Temple at Jerusalem.12