In Response to:
Experienced Foes: The DM should add intelligence to the play of the monsters – they have learned from experience. They can use flaming oil, traps, warning horns, ruses/feints/tactics and surprise, noise distractions and attempts to chase away, and the magic/high quality gear from dead adventurers is fair game. The more intelligent the enemy, the more sophisticated experience they can draw on.
You cannot Play enemies too intelligently. The PCs do not have access to the same level of resources in more advanced editions. DnD basic does not lend itself to gritty realism. The characters have way less hit points and powers than contemporary ones. The idea of a foe ambushing their baggage train and killing retainers and mules that carry their coins and treasure, while intelligent and something that probably would happen, the rules just simply do not ably equip a basic DnD party to handle that well, no matter how much they prepare. It would take a truly experienced group of players and at least second or third level characters to represent that knowledge and not be metagaming to really use intelligent foes to challenge the party.
What characters do have his reliance on the few mechanisms in place. That includes the surrender mechanism whereby they lose treasure and therefore, experience points, in order to bargain for their freedom. While it seems like most foes would never accept such a situation, it is a mechanism that leveraged the known languages of intelligence and that really was only factor intelligence played in the entire game other than as a minimum stat for magic users. That just scratches the surface of how combat oriented and not role-playing oriented. Basic and expert were. With basic being even more so. It really was a kick down the door loot the room sort of scenario that Munchkin the card game is based off of.