The Jargon File (version 4.4.7, 29 Dec 2003):

SPACEWAR
 n.

    A space-combat simulation game, inspired by E. E. ?Doc? Smith's Lensman
    books, in which two spaceships duel around a central sun, shooting
    torpedoes at each other and jumping through hyperspace. This game was first
    implemented on the PDP-1 at MIT in 1962. In 1968-69, a descendant of the
    game motivated Ken Thompson to build, in his spare time on a scavenged
    PDP-7, the operating system that became Unix. Less than nine years after
    that, SPACEWAR was commercialized as one of the first video games;
    descendants are still feeping in video arcades everywhere.


The Free On-line Dictionary of Computing (30 December 2018):

SPACEWAR

    A space-combat simulation game for the PDP-1 written
   in 1960-61 by Steve Russell, an employee at MIT.  SPACEWAR
   was inspired by E. E. "Doc" Smith's "Lensman" books, in which
   two spaceships duel around a central sun, shooting torpedoes
   at each other and jumping through hyperspace.  MIT were
   wondering what to do with a new vector video display so
   Steve wrote the world's first video game.  Steve now lives in
   California and still writes software for HC12 emulators.

   SPACEWAR aficionados formed the core of the early hacker
   culture at MIT.  Nine years later, a descendant of the game
   motivated Ken Thompson to build, in his spare time on a
   scavenged PDP-7, the operating system that became Unix.
   Less than nine years after that, SPACEWAR was commercialised
   as one of the first video games; descendants are still
   feeping in video arcades everywhere.

   ["SPACEWAR" or "Space Travel"?]

   [Jargon File]

   (2004-07-19)