Why Trump is suddenly threatening Iran's last untouched nuclear site

President Donald Trump is threatening to strike Iran’s deeply buried Pickaxe Mountain nuclear facility — a site the United States previously left untouched while bombing the country’s other major nuclear sites , raising new questions about what may have changed. Estimated to lie beneath at least 100 meters of rock near Iran's damaged Natanz nuclear enrichment complex, Pickaxe was designed to replace an above-ground plant capable of assembling roughly 6,000 advanced centrifuges each year before i