In September 2015, Saudi and Emirati forces were coordinating airstrikes together over Yemen. In December 2025, Saudi Arabia was bombing ships sent by the UAE. That reversal, one of the most dramatic shifts in Gulf politics in a generation, did not happen because of a single dispute or a single miscalculation. It happened because two countries that once needed each other have spent years building incompatible visions of what the region should look like, and those visions have