From my understanding (correct me if I'm wrong): Bunker targets (mostly ICBM silos, heavily shielded targets like the bunkers under the White House, etc) would

From my understanding (correct me if I'm wrong): Bunker targets (mostly ICBM silos, heavily shielded targets like the bunkers under the White House, etc) would be targeted with a surface burst because bunkers would withstand air bursts. Soft targets like airports, major cities, factories, ports, etc would be targeted using air bursts to maximize the destruction by preventing the shock wave and direct radiation from being shielded by geography and buildings.