power of speech?

It is explained in Conquest.

The human masters who trained the Apes actually helped Caesar by conditioning the Apes to listen to instruction, however the Apes may have reacted with each order given, and using spoken language. Remember the exchange between MacDonald and Caesar about the emperor moth and how an Emperor Ape, Caesar, would do slightly better. Caesar's intelligence and use of the English language, the same language spoken by the trainers, and Ape language also, made him the "Alpha Ape" and the rest instinctively followed his examples, including trying to speak.


-- I apologize for calling your wife a bloated warthog and I bid you good day. - Connor MacLeod

That's the problem I always had with CONQUEST taking place so soon. I always thought it should've played out a at least a couple of hundred years in the future, giving mankind the opportunity to use genetic experiments to "evolve" the apes closer to how they were in 3955 before they rebell. ESCAPE sets it up perfectly (correcting the error made in BENEATH, which had the nuclear war taking place at the end of the 20th century). CONQUEST could've happened just the way it did in the movie, except having the circus owner (obviously not Armando) bring a descendant of Caesar into the city for the first time. And instead of importing wild apes from jungles, have Ape Management acquire fresh apes from biological labs, results of generations of genetic engineering techniques. Even the TV series had the fall of man take place in the 26th century. It makes a lot more sense that way.

The real problem is Caesar is undoubtedly the first ape who has the intelligence even close to humankind, but the rest of the Apes seem to have caught up dramatically fast in the short period between Conquest and Battle. Apes like Virgil even became a know-it-all.

Cesar taught all the apes how to talk in the events between Conquest and this one