NONFICTION : THE ENCYCLOPEDIA OF MILITARY HISTORY FROM 3500 BC TO THE PRESENT by R. Ernest Dupuy and Trevor N. Dupuy (Harper & Row: $39.95, illustrated).

Should you want to know something about military operations near the Persian Gulf, the Dupuys will take you from the reign of Lugalzaggisi of Erech (died 2325 BC), down to the current war between Iraq and Iran.

Their “series of chronologically and geographically organized narratives” makes a handy reference work, but it’s a trifle old-fashioned. Topics on which much writing has been done in recent years--the economic foundations of war, battle as an experience of common soldiers, the effect of war on civilian society--get left out.

Some assertions are questionable. It isn’t the case, for instance, that at Trafalgar Adm. Horatio Nelson “destroyed French naval power.” The French had plenty of ships left after that battle, and the British continued to fear them.

Every encyclopedia offers a point of view along with the facts. This one tilts to the right. Arms control, for example, comes under the heading “Disarmament,” even though many arms-control advocates have no wish to disarm. And under the Sandinistas, the book says, Nicaragua “became an important conduit in the flow of Soviet arms and munitions from Cuba to the various Central American countries, and particularly El Salvador.” Not a claim the Reagan Administration would object to, certainly, but other observers have.