Yvonne Morris had three minutes to get to work at the start of her shift. Any longer between phoning through her secret code at the perimeter gate and descending a set of stairs and she would have been arrested, at the very least.

Morris was one of the first female crew commanders of a Titan 2 nuclear missile silo. Stationed with the 390th Strategic Missile Wing in Tucson, Arizona between 1980 and 1984, she was responsible for three other crew members and a nine-megaton nuclear weapon.

“Even though our primary mission was peace through deterrence by preventing World War Three,” she says, “in the event we failed, we had to be ready to launch at all times in retaliation.”