Secretary of State Antony J. Blinken arrived in the Middle East on Monday in the hopes of preventing escalating tit-for-tat attacks with Iran-backed militias from spiraling into a broader regional war‚ and to rally allies around a proposed cease-fire agreement for Gaza. Mr. Blinken began his fifth trip to the region since the Oct. 7 attacks in Israel by meeting in Saudi Arabia with Crown Prince Mohammed bin Salman‚ discussing how to achieve “an enduring end to the crisis in Gaza‚” as well as...