From Men & Magic: A quick glance at the Equipment section of this booklet will reveal just how little is required. The most extensive requirement is time.
Yes, time. The above was from the Foreword, two paragraphs in, which proceeds to elaborate upon the referee's duties to their players and the imaginary world they'll spend hours bringing to life. This wasn't Monopoly. Now I can hear the veteran war gamers protesting the laborious setup of their own pastime. No doubt about that. But D&D and all that followed in its wake requires the creation of an entire world, not to mention a very patient referee willing to sit down with their many players. War gaming means setting up and tearing down miniatures, while role playing is the day-to-day life of a universe.
Now I don't mean to denigrate war games, and I understand that many of these are exceedingly complex and border on RPG territory. But Gygax and Arneson, two ardent war gamers if ever there were, understood that their creation was different...
Different enough to qualify the time needed to participate, especially as the new game inevitably brought non-war gamers to the fold. Newcomers who needed to learn what we all take for granted now; namely, that role playing is well worth the time spent on it!