David's Sling and Iron Dome differ markedly, and the differences reflect the types of projectiles they are meant to counter. Iron Dome was designed to defend against short-range rockets and uses Tamir interceptor missiles, which house warheads that explode in proximity to inbound rockets. Iron Dome is well suited for dealing with rockets fired from the Gaza Strip and the Sinai Peninsula, and with shorter-range rockets fired from Lebanon, but it is ill equipped to deal with longer-range rockets — its modest success at defending against the Fajr-5 rockets notwithstanding. Even considering the Fajr-5s, Iron Dome batteries are those best equipped to counter the rocket arsenals of the Palestinian territories, a fact that explains why they are deployed mostly in southern Israel.For its part, David's Sling is capable of intercepting artillery rockets with ranges of 70 to 300 kilometers (approximately 45 to 185 miles). Developed jointly by Israel's Rafael Advanced Defense Systems and the United States' Raytheon, the system uses two-stage Stunner interceptor missiles that, unlike the Tamirs, hit inbound rockets directly and destroy them with sheer kinetic impact. The Stunner is also larger than the Tamir, and with its more sophisticated guidance and propulsion systems it can travel farther. David's Sling eventually will be able to intercept unmanned aerial vehicles, short-range ballistic missiles and cruise missiles.
A Superior Arsenal
As Operation Pillar of Defense showed, Israel feels threatened by the presence of rockets in the Gaza Strip. But an even greater concern for Israel is Hezbollah, the Shiite militia in Lebanon, which has far more and far better rockets than do Palestinian militants in Gaza. Hezbollah's inventory is thought to hold 100,000 rockets, ranging from 122 mm BM-21 type rockets to the much larger and longer-range 610 mm Zelzal-2 rockets. According to unconfirmed reports, the group may have even acquired Scud missiles from Syria. Hezbollah leader Sheikh Hassan Nasrallah may have alluded to these weapons during his Ashura speech on Nov. 25, when he said Hezbollah could strike as far away as Eilat in southern Israel.
Hezbollah has enough rockets to overwhelm Iron Dome defenses. (Israel would need to deploy 10-15 batteries for full coverage.) Before reloading, each Iron Dome battery holds a maximum of 60 Tamirs, which are often fired in waves to ensure interception. Even if Iron Dome's purported 84 percent success rate were maintained, there would not be enough interceptors available to stop all short-range rockets from Lebanon. After all, during Operation Pillar of Defense dozens of rockets still managed to strike Israel.
An Option for Defense
Israel understands the threat posed by Hezbollah's large rocket arsenal and recognizes that it has few options to mitigate it; David's Sling is one such option. While Hezbollah and Hamas collectively boast an impressive arsenal of rockets, the vast majority of those rockets are short range. This makes the arsenals much easier to conceal from Israeli intelligence, surveillance and reconnaissance efforts. Fajr-5s and Zelzals can travel farther and are more powerful, but they are also more visible and thus more vulnerable to detection and subsequent air and missile strikes.
In fact, the Israeli air force targeted Hezbollah's long-range rocket arsenal at the outset of the 2006 Lebanon War. The air force likewise targeted Hamas' longer-range rocket arsenal at the outset of Operation Pillar of Defense. How many of those rockets were destroyed is questionable: In 2006, Israel claimed to have destroyed some two-thirds of the rockets, and in 2012 Israel claimed to have destroyed the majority of the Fajr-5s even though Hamas continued to fire them at Israeli territory. Nevertheless, it is clear that Israel has been far more successful at detecting the longer-range rockets than the smaller ones.
Short-range rockets will always be difficult to contend with. Given their abundance, particularly in Lebanon, they could oversaturate Iron Dome's short-range air defense network. But Arab militants would find it appreciably more difficult to oversaturate David's Sling's mid-range defense network — simply because they do not have enough rockets to do so.
For these reasons, the development and eventual deployment of David's Sling marks a milestone in Israel's continued efforts to protect itself from rocket fire. However, no system can provide Israel with full protection in a full-scale war, and Israel's enemies will continue to pursue more advanced weapons and to shift their tactics. Ultimately, Israel will have to continue to rely on the threat of a combined land and air invasion to deter militants within its neighbors' borders.