Does Advanced Dungeons & Dragons have rules for holding/delaying action in combat?
Awaiting Action Page 63 1st edition Dungeon Master Guide. Like Gygax said the title is self explanatory. Note it is under Encounter Reactions but it and the other encounter reactions are listed a possible choices when you gain initiative.
Personally I allow a player to hold their initiative allowing them to interrupt another player or monster until the round is over. I do this with either party or individual initiative.
Somewhat related I allow players to do a cover as well. They make an attack and if successful they don't do damage. Instead they have the target covered and may interrupt any action short of an instantaneous effect and immediately complete the attack doing damage. This allow them to the knife at the throat type maneuvers without introducing a lot of complexity to AD&D combat.
No, nothing's in the rules. :)
However, adding a "Hold" option doesn't seem to harm or abuse the initiative system. In its most common application, "Hold" means the character may start to act at any time thereafter (whether you're calculating sequential events strictly by segments or in a less precise mode) simply by saying so, 'jumping in' as it were. An 'attack of opportunity' (harkening back to the original use of the term in the wargaming roots of AD&D) is a classic example, and the principle thus has adequate pedigree.
The time required to complete the stated action is either defined (casting time, weapon speed) or fairly adjudicated by the DM, either being calculated from the point at which the player exercises the option subsequent to the "Hold" declaration.
Of course if a character Holds and then does not exercise any option, the character has no action that round.
I don't think I've ever seen a delay mechanic in AD&D2. I've never played AD&D1. In our group, however we have typically declared the action as going on delay with an exit condition.
Example: I'm going to delay either until I get shot and need to take cover, or the bad guy comes out of his cover, then I'll let shoot him with my crossbow.
Typically if a character holds delay across multiple rounds, s/he gets to choose when to come out of delay. To include acting BEFORE the highest rolled initiative (since his is actually the initiative of last round) of a given round. But he would not get to roll for init on this particular round (since s/he has acted already).