As America begins to discuss building walls to stop illegal immigration, here’s some harsh but very pragmatic advice from an Israeli expert, at Ha’aretz: Israeli advice on the Mexico fence: be ruthless. (Hat tip: Jim.)

Money: It will probably cost more than you think. Why? Because that’s always the way it is with such projects. Americans, the Israeli says, tend to be very structured in their work, in a way that has many benefits but also some limitations. It means that they waste a lot of money on “process” and “management” and “studies” before they really act. They make no short-cuts, thus save no money. In the last issue of The National Journal, the Israeli fence is mentioned as the example to use when calculating the cost of such a fence (2000 mile fence = $6.4 billion dollars). The Israeli expert thinks the Americans will end up paying more.

Efficiency: It can work, the expert says - and other Israeli know-hows agree. Don’t buy the argument of liberal opponents who say “no fence can stop people from coming.” If done in a proper way, the fence can work. It can achieve whatever goal the U.S. wants it to, “100 percent, 90 percent, 80 percent prevention. Just make the right commitment and you?ll get results.”

Tactics: Don’t just rely on sophisticated machinery and equipment. You need people on the ground using the equipment to pursue the invaders. They need to react fast, they need intelligence, and they need to be tireless. It will only take a couple of months before the flow of immigrants will become much weaker.

Intelligence: Recruit people on the Mexican side to be your eyes and ears and to tell you what the smugglers are up to. Make sure you can communicate fast, and react even faster. Good intelligence can be the key factor for success.

Routine: The smugglers will be inventive and will look for ways around you. If you stick to some regulated routine, you’ll end up wasting your time and your money. Surprise them where they don’t expect you, make them understand that no place is safe, no route out of reach. “Don’t police them, fight them.”

Ruthlessness: Is it really important for the Americans? If it is, they should be prepared to show it. “Make the other side understand that this is no game - that life can be in danger,” says the expert. “I know this is the toughest advice of all, but short of doing it the Americans will end up pretending to stop illegal immigrants rather than really doing it. At the end of the day, it is very simple: America is more powerful than the smugglers - meaning, it can deter them from doing what they do.” But there’s one condition necessary to keep this preponderance of power working: “It should be as important for America to stop the illegal new comers as it is for them to come.”

Danger: You mean they have to shoot the smugglers? “No, they have to stop them. But if they run away they have to chase them, and if they resist they need to use force. Eventually, they’ll end up doing things you don’t want people to watch on television. I’m not sure if they have the resolve and the stomach to do it. Maybe it’s not as important for them as they claim it is.”