What I mean is, what is so safe about the hills? Google yielded only scant definitions (flee) or links to Iron Maiden lyrics.
If you hide up in the hills it makes it harder for the enemy to find you, just because the hilly terrain makes it more difficult for the enemy to see you (note that this still applies even today, just look at Afghanistan). So, if you are going to be running away, heading for the hills is a good place to go.
From Sun Tzu’s Art of War:
“If the enemy holds the high ground, do not ascend and do battle with him… Generally, the army prefers high ground and dislikes low ground”
The hills are also easier to defend - plenty of high ground, rocks to hide behind, valleys to outflank your enemies from.
Also handy in case of flood.
The terrain sharply limits the mobility of a persuing force, plus residents familar with where passes and shortcuts are can outmaneuver invaders.
While all the answers given sound good, they all overlook one simple fact: the popularity if the expression comes from the Bible, and has nothing whatsoever to do with fleeing from an enemy or fighting an enemy or evading floods.
The reason for fleeing to the hills is simple: the world is going to be destroyed and everybody associated with it is going to be destroyed. Only by going into the wilderness and disassociating themselves with Judea that people will be saved. It’s attempting to draw an obvious parallel with Lot and his family, who were likewise ordered to leave a condemned city and flee to the hills, not looking back.
The expression, at least in English, has no connection whatsoever to fleeing armies, or geurilla war or evading floods. It’s just another Biblical passage that we’ve adopted and forgotten the origin of.
Al Quida and Bin Laden know the value of hills. And so does Saddam Hussein.
Hilly/Mountainous terrain just provides many more good places to hide.
This thread reminds me of this Python sketch.
Except that’s not Python sketch.
Is that not where the Hills Bros. Coffee is kept?
Head for the Hills, trademark, 1959. Trademark cancelled 2003.
USPTO
The jump from flee into the hills to “head for the hills” seems to be stretching the supposed Biblical origin somewhat. It’s not a passage that leaps into the common folk memory, unlike, say, Pride goeth before destruction and an haughty spirit before a fall.
Though it’s not without problems, as I understand it. High ground and valleys and whatnot isolate your own forces, and can make it difficult for them to reinforce each other. If things go badly, you can end up with a bunch of isolated pockets of soldiers that your enemy can mop up with overwhelming force at his leisure.
Close enough. I don’t remember if it’s from The Secret Policeman’s Ball or The Secret Policeman’s Other Ball, but both shows featured Python players and were directed by John Cleese.
I remember hearing that during the 2004 tsunami there were some communities that had passed down the advice through their culture that if the water recedes from the beach, you run for the hills. The story went that those communities did so and survived the tsunami. Don’t know if that’s true and I doubt it’s relevant to the western expression you’re asking about but it’s interesting. 
I don’t think that people are “running for the hills” in order to do battle there. You never hear the expression used to say “let’s go to a fortification and prepare to fight”. The point of the expression is to scatter, to flee, and to not come back.
It’s just because people tend to live in valleys, where the rivers are, not in mountains. If you live in a mountain range, you probably live between two or more hills, not on their peaks. So “run for the hills” means to flee the city/town where a battle is about to go down. If people lived in the mountains (they don’t), then the expression would be “run/head for the valley!”
My WAG would be it came from moonshiners who would head for the hills when the Revenue men showed up.
I think the “high terrain” aspect may be a bit misleading here. AFAICT, “run for the hills” isn’t much different from “take to the tall timber”, both meaning “to flee, evade danger”.
The “hills”, like the “tall timber” or forests, simply stand for more remote and less populous places, where you’re more likely to be able to hide in safety.
Was Saddam’s hole in the ground on a mountain? Hadn’t heard that.
I would have thought anything Saddam may or may not have known would have converted to the past tense when he died.
Do you know something the rest of us don’t?