India is hiring several Israeli defense firms to work with DRDO (the Indian Defense Research and Development Organization) and several state-owned defense firms to design and build an integrated anti-missile defense system. India already has a tested and proven anti-missile ABM (Anti-Ballistic Missile) but wants something like the anti-missile system Israel has developed and deployed over the last two decades. This may involve buying the latest models of Israeli Green Pine radar, which is a key element of the Israeli anti-missile defenses.
In late 2013 India conducted a final round of development tests of its ABMs. This involved intercepting multiple incoming ballistic missiles and was declared a success. As a result of this, and several other successful earlier tests, Indian missile development officials declared that their anti-missile missiles were ready for mass production and deployment. This would provide some Indian cities protection from Pakistani or Chinese ballistic missiles. But the Indians realized that just having a reliable interceptor missile was not enough. You needed an integrated communications and radar warning system. The Israelis and the Americans are the only ones with years of experience with such anti-missile systems and India was already a steady customer for Israeli weapons and electronics systems.
The Indian anti-missile missiles come in two sizes. The Prithvi Air Defense (PAD) missile is the larger of the two and is used for high altitude (50-80 kilometers up) interception. The short range Advanced Air Defense (AAD) missile is used for low altitude (up to 30 kilometers) intercepts. The two missiles, in conjunction with a radar system based on the Israeli Green Pine (used with the Arrow anti-missile missile), provide defense from ballistic missiles fired as far as 5,000 kilometers away. A third interceptor, the PDV, is a hypersonic missile that can take down missiles as high as 150 kilometers and is still in development. India is the fifth nation to develop such anti-missile technology.
The Indian system has been in development for over a decade. Back in 2003 India ordered two Israeli Green Pine anti-ballistic missile radars. That equipment was used in 2007 in one of the first successful Indian tests, where one ballistic missile was fired at another "incoming" one. The Israeli Green Pine radar was originally developed for Israel's Arrow anti-ballistic missile system. Arrow was built, in cooperation with the United States, to defend Israel from Iranian and Syrian ballistic missiles. India has since developed, with Israeli help, the Swordfish radar, which has similar capabilities to the Green Pine and has been operational since 2011. Swordfish is part of a system that integrates data from satellites and other sources in order to detect and track incoming missiles.
The interceptor missiles and the fire control systems were designed and built in India, although more Israeli technology may have been purchased to speed things along. India wanted to buy the entire Israeli Arrow system but the United States refused to allow the sale (which involved a lot of American technology). The new deal with Israel is apparently supposed to get around those restrictions.
The Indian ABM system wasn’t supposed to become operational until 2015. But the developers believed it was ready in 2014 and asked parliament for money to start building systems to defend places like New Delhi (where parliament is). At that point there was a debate over the state of the Indian technology and some Indian officials doubted that the ABM system would be operational, even if just around New Delhi using just Indian technology. Questions were asked about just how effective the Indian ABM system really was. India has a shabby reputation with developing weapons. Projects go on for decades, often passing tests but without ever producing operational weapons. Joint-ventures with other countries (like Russia, France, and Israel) have been more successful. Israel was apparently more heavily involved with the Indian ABM than official pronouncements indicated. So it made sense to go public with heavier Israeli participation to get the Indian ABMs operational. If nothing else that would scare, or at least annoy, the Chinese more.
If the new system works China and Pakistan could only defeat it by firing more missiles simultaneously than the Indians could handle. It's also possible to equip warheads with decoys in an attempt to get the interceptor missile to miss. Israel has technology designed to deal with these decoys and India was attracted to that. But against an overwhelming number of incoming missiles, some are going to get through. Yet if you have a defensive system and the other guy does not, you have a big advantage no matter what.