But this conflict will ultimately be ended not by bullets or bombs, but by backchannel diplomacy. And as Switzerland’s former ambassador to Iran — where I officially represented Washington’s interests in Tehran — I know what it’ll take for both nations to ink a peace deal. For more than 150 years, Switzerland has served as a trusted go-between for countries without diplomatic ties, often acting as a “protecting power” and mediating between hostile governments. We first took on this responsibility during the Franco-Prussian War of 1870 — the period from which the modern institution of protecting power originates. Since then,...