Why in News?

• • In December 2021,  the first unit  of S-400  is expected to be operational .

• The acquisition has the potential to cause a diplomatic rupture between the US and India when the two countries are on a path to a tighter relationship.

What is S-400?

• Considered one of the most advanced and potent air defence systems in the world, S-400 Triumf has the capability to protect against almost all sorts of aerial attacks, including drones, missiles, rockets and even fighter jets.
• The system, intended to act as a shield over a particular area, is a long-range surface-to-air missile system.

How does it work?

• S-400 detects an aerial threat approaching the air defence bubble (the area it has to protect), calculates the trajectory of the threat, and fires missiles to counter it.
• It has long-range surveillance radars that send information to the command vehicle. On identifying the target, the command vehicle orders a missile launch.
• Think of the Iron Dome, recently used by Israel to protect against incoming rockets from Gaza May. Only, S-400 has the capacity to protect a much larger area from threats that are much farther.

Why has India bought them?

• To protect against attacks by missiles, or fighter jets from China or Pakistan

• A report by the think tank Observer Research Foundation mentioned that there is no alternative system capable of serving its long-range air defence requirements, from the standpoint of either capability or cost.
• The report compared S-400 with the American MIM-104 Patriot system, which it noted is “primarily oriented toward missile defence with less focus on the pure anti-aircraft role”.
• It said S-400 can be deployed within five minutes, compared to 25 minutes for Patriot (PAC-3). It has a speed of 4.8 km/s compared to 1.38 km/s. 
• It is cheaper too, with a per-battery cost of approximately $500 million, compared to the Patriot’s $1 billion.

Why is the US upset with it and India’s Response?

• There are several reasons. One is that the US wants India to wean off its traditional reliance on Russian defence systems. 
• Russia has been the largest defence partner for India over the decades, a relationship that is changing as India inches closer to the US diplomatically and strategically; imports from the US have gone up, largely at the cost of Russian imports.
• But the larger cause of concerns about the deal for Indo-American relationship lies in a 2017 law passed by the US named Countering America’s Adversaries through Sanctions Act (CAATSA), whose objective is to counter American adversaries Iran, Russia and North Korea through punitive measures. 
• Title II of the Act deals with sanctions in Russian interests, including its defence industry. The Act empowers the US President to impose at least five of the 12 listed sanctions mentioned in Section 235 on persons who engage in a “significant transaction” with Russian defence and intelligence sectors. 
• The US imposed sanctions on Turkey, a longstanding NATO ally, in December 2020 over its purchase of the system.
• In January, a US Congressional report warned that if India goes ahead with the purchase of the S-400 system, it may lead to sanctions. The report warned that “India’s multi-billion dollar deal to purchase the Russian-made S-400 air defence system may trigger US sanctions on India” under CAATSA. A few days later, the outgoing US Ambassador to India Kenneth Juster raised issues of “interoperability” between the forces of the two nations, which was viewed as a veiled reference to the S-400 deal.
• India’s External Affairs Ministry responded that “India and the US have a comprehensive global strategic partnership” and “India has a special and privileged strategic partnership with Russia”. The ministry said “India has always pursued an independent foreign policy. This also applies to our defence acquisitions and supplies which are guided by our national security interests.”

Reference:

1. https://indianexpress.com/article/explained/s-400-purchase-air-defence-system-india-us-relation-7626388/