Israel’s missile defences blunt Palestinian attacks from Gaza
THE NIGHT sky above Israel’s Mediterranean coast on May 11th was like a cosmic football match, as fiery shooting stars tried to outrun and catch each other; fireballs marked successful shots. Hamas and Islamic Jihad, two militant Palestinian groups, have fired more than 1,000 rockets from Gaza, at targets including the greater Tel Aviv area, Israel’s main metropolis and home to 4m people. Israel’s Iron Dome missile-defence system has been trying to shoot them down—with considerable success. Only a handful of rockets have got through to hit built-up areas. Despite the barrage, Israeli deaths remain in single digits.The fear is that this aerial battle is the precursor to an all-out war, involving a ground invasion of Gaza by Israeli troops. Already more than 50 Palestinians, including a senior Hamas commander, have been killed by Israel’s bombing campaign.Avoiding further escalation depends partly on Iron Dome’s success. “What you’re seeing in the sky is the algorithm,” explains an engineer involved in the development of the system. “We’ve been constantly improving the algorithm so it can face a barrage like this.” It’s not just mathematics, though, behind what the Israeli armed forces claim is a 90-95% rate of interception.The Israeli air force deployed its first Iron Dome batteries just over a decade ago with the intention of protecting its bases, rather than shielding civilians. The first interception of a rocket fired from Gaza was in April 2011. The system, developed by Rafael, an Israeli defence contractor, with substantial financial help from America, uses radar, as well as other sensors, to detect the launch of incoming rockets. Its command-and-control computer systems plot the trajectory of the rockets, working out whether they are heading for a built-up area. The “Tamir” interceptor missiles are then launched to knock out the threatening ones by exploding next to them.In the ten years since Iron Dome first proved its worth, Palestinian militants in the Gaza Strip, blockaded by Israel and Egypt, have been trying to come up with ways to defeat it. Most rockets from Gaza are fired in smaller numbers at nearby Israeli towns and villages. The barrages this week of dozens of rockets at a time, aimed at a large urban area—Hamas claimed to have fired 130 in one go on May 12th—mark the latest attempt to overwhelm the system, whose radar and computer systems have to work harder to calculate the trajectories of a large number of incoming projectiles.“When they’re firing at a big city like Tel Aviv, there’s no question: you intercept every incoming rocket,” says Isaac Ben-Israel, a former major-general once in charge of Israeli weapons development. “They failed because this is specifically what the system was designed to do: deal with multiple targets; and it’s constantly been improved so it can deal with more.”Though Iron Dome’s technology has proven itself, the system still has limitations. One is the economics of missile defence. Despite improvements in recent years that have increased their range and explosive payload, Palestinian rockets remain relatively rudimentary and cheap to produce, with Iranian guidance, from metal irrigation pipes in workshops in Gaza. By contrast, each Israeli interceptor missile is estimated to cost around $40,000, though a recent agreement with Raytheon, a weapons manufacturer, to set up an assembly line in America will bring the price down. Even so, each interceptor will always cost many times more than the rocket it is intended to destroy.According to Israeli intelligence, before the clashes began Hamas and Islamic Jihad had around 13,000 rockets in Gaza. They are thought to have already fired nearly 10% of them in two days of fighting. Israel has built up a large stockpile of interceptors in recent years. But the number is classified and in the last big clashes between Israel and Gaza in 2014, which lasted for 51 days, the inventory ran low.Israel is also trying to stop the attacks at source. It has already bombed about 200 launching sites, but there are still many more; lots of them are in residential areas, and so not easy to hit without causing civilian casualties, and so incurring international opprobrium. Separately, it is trying to inflict pain on the militant groups by killing their leaders and disrupting their organisation, but this tactic runs into the same problem: Israel has destroyed three tower blocks in Gaza, in operations reportedly aimed at Hamas offices (it gives inhabitants warning to flee).The latest round of fighting began on May 10th, when Hamas fired rockets at Israel in response to clashes between Israeli police and Palestinian protesters at the al-Aqsa mosque in Jerusalem. So far neither side seems to be running out of rockets or missiles, or the desire to fight.Some Israeli defence experts argue that it would make more sense to develop a directed-energy interceptor, like a laser. Last year Israel’s defence ministry boasted that the country was “among the leading countries in the field of high-energy laser systems.” The advantage of such technology—if it can be shown to work— is that it is cheaper, per shot, and never runs out of ammunition. Yet plans for investment are on hold because of Israel’s political paralysis; no new state budget has been approved for the past three years.Another weakness of an Iron Dome battery is that it covers only a limited area, estimated to be around 100-150 square kilometres, or the size of a large town. This means that Israel needs to shuffle around the batteries it has according to its assessment of risk (one Palestinian tactic has been to shift the direction of rocket launches). There have been disputes over the years between politicians and generals over whether the highest priority in wartime should be given to protecting civilian areas or the military air bases needed to pursue the fighting. In a future war with Hizbullah, the Lebanese militia-cum-party that has a far larger and better missile arsenal than Hamas, such trade-offs might be unavoidable.These limitations mean that Iron Dome would be less useful for a country with significantly larger territory than Israel. Consequently, Israel has not been very successful in exporting the system. So far it is reported to have been purchased by Singapore, a small city-state, and America’s army has recently bought two batteries to protect overseas bases.“The main strategic advantage of Iron Dome is that by significantly reducing Israeli civilian casualties, it allows the political leadership to pause before committing to all-out war,” says one Israeli general. “There’s no perfect weapon to prevent all casualties,” he adds. “For that you need peace”.But for now, peace does not seem either side’s favoured option. Israeli leaders have rejected a ceasefire and vowed to strike Hamas hard. Indeed, the only way to prevent rocket launches altogether is to occupy the launch sites. The last time Israeli forces entered Gaza on the ground was in 2014, and even then it was only a limited re-occupation. Israeli infantry and armoured battalions have already been gathering at staging-grounds around Gaza, in preparation for such an eventuality. But the Israeli government remains anxious to avoid it. Close-quarters fighting in built-up areas would favour the militants, and would involve many more casualties on all sides. Binyamin Netanyahu, Israel’s prime minister, will be hoping that he can win the match in the air.