Anticipating a disaster in the invasion of Normandy in 1944, Dwight Eisenhower drafted a speech announcing that the invasion failed.
Realizing the strong chance that the moon landing would not succeed in 1969, William Safire, a speechwriter for President Nixon, drafted a speech emphasizing the bravery of the astronauts who risked their lives.
An advisor to Queen Elizabeth drafted a speech for a nation under attack in nuclear war.
Fortunately, these speeches never had to be delivered. But Archie Bland in the (UK) Independent excerpts them and reflects:
"Such artefacts are a powerful warning never to get too comfortable. They show us how perilously close this world is to not existing as we know it, how radically it can change, and how suddenly."