Education
"Intelligent" is not the same as "Educated". Any average person can learn about military tactics and the history of warfare, but few do. Those that do will be at a SIGNIFICANT advantage.
Consider this: You and three of your buddies (none of whom have any military expertise or experience with guns) are given assault rifles and 6 months. At the end of the 6 months four soldiers who have received years of education in military tactics and warfare and extensive training - not to mention a greater variety of weapons at their disposal - will come to your neighborhood to try to kill you. Who do you think will win? Despite what TV would have you believe, the odds-on winners are going to be the military guys. Not because they have any physical or mental capabilities that you could not learn, but because they have received physical and mental training which you did not receive.
For lack of knowledge about them, I actually expect the tanks and most any large munitions to be useless to the apes. Tanks are more complicated than cars, but let me make an analogy here. Unless you have been educated to understand that you need to insert a small piece of metal with odd ridges into a similarly-sized slot near a car wheel and turn it, you will never get a car to start in the first place to be able to figure out how to drive it. Seriously - go find someone who has lived in a jungle their whole life and give them a car and tell them to drive it, leaving the key nearby on the ground. They will never get that car moving.
Munitions are a similar story, but they can probably be worked out. Unfortunately, many of the apes who tried to figure out how to use them were killed in the attempt. That's pretty demoralizing and might well lead to a "let's just leave those alone" stance.
And speaking of that... the humans should fight SMARTER and not HARDER
Let's consider what to do formfrom the perspective of a human being that knows a bunch of darned, dirty apes are waiting for a fight in the forest. I could walk in and engage them, but instead I think I'll just burn it to the ground. Similarly, for the apes in the city I'm going to start with some bombardment. I won't get them all with either action, but I'll get enough that the numbers are going to tilt noticeably in my favor.