One bomb, two ceasefires: From Iraq to Iran, how the US's 30,000-pound bunker buster GBU-28 ended two wars, 30 years apart

The US has once again turned to its bunker-busting arsenal, this time targeting Iran's nuclear sites with GBU-57 bombs dropped from stealth B-2 bombers. The attack echoes a similar moment in 1991, when a hastily-built GBU-28 penetrated Saddam Hussein's final stronghold in Iraq. From Gulf War innovation to modern-day military doctrine, these earth-penetrating bombs have come to symbolise America's message: even the deepest shelters aren't safe.