[Editor's note: This was first written on May 21 and is being reprinted with permission]

The news last week that the Obama administration was asking the US Congress to approve $205 million for the "Iron Dome" rocket defense system was an important development. Israel has gone through two wars in 2006 and 2008 in which both Hizbullah and Hamas launched rockets at Israeli civilians living in towns and moshavim. The reports in the American and Israeli media also inferred another motivation for Washington supporting the Iron Dome project: once an anti-rocket defense system is operational, the prospects of Israel re-deploying from West Bank land will increase, since Israeli officials in the past made the existence of such a system a pre-condition for future Israeli withdrawals. A senior administration official, in a conversation with American Jewish leaders, reiterated last Thursday that Iron Dome was necessary for the two-state solution.

But is it correct to assume that if Israel can effectively intercept short-range rockets like the 7 kilometer range Qassam rocket or the 12 kilometer range Grad, then it can withdraw from the West Bank, assured that the potential rocket threat has been neutralized? The truth is that the situation is far more complicated than the way it is usually presented. It should be recalled that Hamas developed the Qassam rocket in the Gaza Strip when the area was still under the Palestinian Authority. The first Qassam was fired at Israel in 2001, well before Hamas kicked out the PA from the Gaza Strip in 2007. It is likely that if a Palestinian state is created in the West Bank, then there will be Palestinian organizations which will produce Qassam rockets in their own factories and workshops, just like they did in the Gaza Strip. Ben Gurion Airport would be in range of a Qassam rocket attack from West Bank villages near the Green Line, like Budrus and Rantis.

Even if Israel has an Iron Dome defense system in place protecting Ben Gurion Airport in the future, how would international airlines react knowing that the Qassam threat to their aircraft existed, the rocket defense system notwithstanding? If the Palestinian organizations in the West Bank construct hundreds of rockets, as they did in the Gaza Strip, and aimed them at Ben Gurion Airport, would Air France, British Airways, and Delta continue to fly into Israel and risk their aircraft--reassured that "Iron Dome" would take care of the rockets? Would the large international insurance companies increase the premiums that airlines would have to pay to such a level that their continued flights into Israel would simply be too expensive? It is the existence of an immediate offensive threat against Israel's vital national infrastructure that will determine whether global corporations decide that Israel is safe and not the existence of rocket defenses. No one would want to visit a country where there is shooting in the streets even if every tourist was given a bullet-proof vest when he arrives at the airport.
 
What the development of the "Iron Dome" system demonstrates is that what experts call "deterrence by punishment" has only limited utility against rockets launched by terrorist organizations from populated areas. Thirty years ago Israeli political leaders would speak confidently that if Israel withdrew from territory and afterwords the Palestinians fired into Israeli towns, there would be a painful Israeli retaliatory response they would not forget. "Deterrence by punishment" is still relevant against countries like Syria, if it ever launched a missile into Tel Aviv. But smaller rockets turn out to be a different story. In the case of the Gaza Strip, it took eight years before Israel responded with decisive force to rocket attacks. And even while the IDF was fully justified to go into Gaza in Operation Cast Lead, it faced unprecedented international criticism as well as a Goldstone Report. Anyone thinking that Israeli can easily invade a Palestinian state in the West Bank, after rockets are fired on Israel is making a mistake.
 
The alternative form of deterrence that Israel needs is "deterrence by denial"--that denies the enemy from achieving his objectives. Rocket defense systems are only part of the answer. What Israel learned in the Second Lebanon War in 2006 was that the only way to prevent short-range rocket attacks was by controlling the ground from where the rockets were being launched. That is why after it used air power unsuccessfully to suppress Hizbullah rocket attacks, the IDF decided to move in force on the ground to seize Hizbullah launch areas in Southern Lebanon. In the Palestinian case, Israel may not be able to control every potential launching area if it reaches an agreement with the Palestinians, but it can insist on retaining the most probable areas that would be used by Palestinian rocket teams in the terrain dominating Ben Gurion Airport and other parts of Israel's national infrastructure. A special team sent two years ago by Secretary of State Condoleezza Rice sought alternatives to control of the ground around the airport, but could find none.
 
At the same time, while neutralizing the threat of domestically-produced Qassam rockets, Israel must secure the points of entry into the West Bank, in the Jordan Valley, through which longer-range rockets, like the Grad, might be smuggled. The deployment of the "Iron Dome" system is a necessary condition for Israel taking the risks of any further withdrawals, but it is clearly not a sufficient condition for protecting Israel.