The Israeli military recently reminded the public that the Iron Dome anti-rocket system was not meant for defending towns and villages but military bases and critical infrastructure (power and water). This reminder comes after Iron Dome successfully defeated a Hamas attack (using 1,500 rockets) last November. Many Israelis assumed this meant they could expect similar protection if there were a larger attack from Hamas or Hezbollah. But the military points out that Hamas has over 5,000 rockets and Hezbollah over 40,000. If one or both of these groups fired several thousand rockets the Iron Dome batteries would have to be used to defend military bases and power plants first (otherwise defense of the nation would be imperiled) before trying to cover civilian targets. With a smaller attack the existing number of Iron Dome batteries is sufficient to defend everything, which is what happened last year. But until it is possible to buy more Iron Dome batteries, a major attack will leave many civilian targets vulnerable.
This is not the first time the military has pointed this out. The first time was three years ago, in response to announced plans to keep the new Iron Dome batteries in storage. At that time politicians were making much of using Iron Dome as a means of defending civilians living close to the border and vulnerable to rockets fired from Gaza in the south and Lebanon in the north. But it turns out that it takes about 15 seconds for Iron Dome to detect, identify, and fire its missiles. Most of the civilian targets currently under fire from Gaza are so close to the border (within 13 kilometers) that the rockets are fired and land in less than 15 seconds. When longer range rockets are fired there are many more targets (civilian and military) to aim at and Iron Dome is effective. This is what happened last November.
This explains why, after Iron Dome was declared ready for action three years ago, it was surprisingly placed in storage. The air force said they would prefer to save money and put the Iron Dome batteries in storage, to be deployed only for regular tests (and for training) and for an actual emergency (an expected large scale attack on southern or northern Israel). Politicians demanded that at least one battery be deployed along the Gaza border. The military sees Hamas and Hezbollah stockpiling larger numbers of longer range rockets that would enable massive use of long-range rockets against military bases. The generals believe it's more important to protect the military forces, who ultimately defend Israel, and that's what Iron Dome will now be used for.
Since 2010, Israel has bought seven batteries of Iron Dome anti-rocket missiles. Five are in action and were responsible for defeating the Hamas attack last November, which used a lot of long range rockets. Each battery has radar and control equipment and four missile launchers. Each battery costs about $37 million, which includes over fifty Tamir missiles (costing $40,000 each). Iron Dome uses two radars to quickly calculate the trajectory of the incoming rocket and do nothing if the rocket trajectory indicates it is going to land in an uninhabited area. But if the computers predict a rocket coming down in an inhabited area, guided missiles are fired to intercept the rocket.
This approach makes the system cost-effective. That's because Hezbollah fired 4,000 rockets in 2006, and Palestinian terrorists in Gaza have fired over six thousand rockets in the past eight years, and the Israelis know where each of them landed. Over 90 percent of these rockets landed in uninhabited areas, and few of those that did hit inhabited areas caused casualties. Israel already has a radar system in place that gives some warning of approaching rockets. Iron Dome uses that system, in addition to another, more specialized, radar in southern Israel.
The Palestinians are believed to have tried to defeat Iron Dome by firing a lot of long range missiles simultaneously at a few cities. In theory this could overwhelm one or two Iron Dome batteries. But Israel is able to keep 24/7 UAV watch on Gaza and spot attempts at large scale simultaneous launchers. This enables Israel to bomb many of the launch sites. This results in many rockets destroyed on the ground or launching erratically and landing within Gaza or nowhere near where they were aimed. Because Iron Dome can track hundreds of incoming missiles, quickly plot their trajectory and likely landing spot, and ignore the majority that will not land near people, the Palestinians tried putting hundreds of larger (long range) missiles into the air at the same time to be sure of causing lots of Israeli casualties. So far the Palestinians have not been unable to get enough rockets into the air at the same time.
The Palestinian rocket attacks have been around since 2001, but got much worse once Israel pulled out of Gaza in August of 2005. This was a peace gesture that backfired. From 2001 to 2005, about 700 rockets were fired from Gaza into Israel. Since the 2005 withdrawal, over 5,000 more rockets were fired into Israel. The rate of firings increased after Hamas took control of Gaza in June, 2007.
Hamas has been bringing in more factory made Iranian and Chinese made BM-21 and BM-12 rockets. Israel believes Hamas currently has, in Gaza, factory-made BM-21 rockets, each with a range of 20-40 kilometers. They also have some shorter range (six kilometers) Russian designed B-12 rockets. The 122mm BM-21s weigh 68.2 kg (150 pounds) and are 2.9 meters (nine feet) long. These have 20.5 kg (45 pound) warheads but not much better accuracy than the 107mm model. However, these larger rockets have a maximum range of 20 kilometers and a flight time of under 15 seconds. Again, because they are unguided, they are only effective if fired in salvos or at large targets (like cities, large military bases, or industrial complexes).
There are Egyptian and Chinese BM-21 variants that have smaller warheads and larger rocket motors, giving them a range of about 40 kilometers and flight time over 15 seconds. Israel believes there are dozens of even larger Iranian Fajr rockets, with a range of 70 kilometers, plus several hundred extended-range (40 kilometers) 122mm rockets, and even more standard range (20 kilometers) 122mm rockets in Gaza. Before last November there were thought to be over 10,000 rockets stored in Gaza. But between Iron Dome and attacks on storage sites by artillery and smart bombs, over half of those rockets were destroyed.