William A. Wellman was offered Gen. Williams.
In his memoirs, Charlton Heston says he was asked to play the lead.
Though it follows the general plot rather closely, there are a number of differences between this adaptation and the original novel by Alistair MacLean. Notably among them, in the novel the action is set in the UK, Sation Three is called the Mordon Microbiological Research Establishment, George Maharis' character is called Pierre Cavell and Anne Francis' character is called Mary and is actually married to George Maharis' character.