The original Dungeon Master's Guide was published in 1979, and gave Dungeon Masters everything they needed to run a D&D game campaign. The Player's Handbook, Dungeon Master's Guide, and Monster Manual are collectively referred to as the "core rules" of the Dungeons & Dragons game. While all players, including the Dungeon Master, are expected to have at their disposal a copy of the Player's Handbook, only the Dungeon Master is expected to refer to the Dungeon Master's Guide or Monster Manual during gameplay.