India and Russia signed agreement on S-400 missiles in October 2018 to acquire five units of the S-400 triumph to air missile system, in defiance of the US's thread to impose sanctions under 2017's countering America Adversaries through sanctions Act.
This advanced air defense system significantly enhances India's air power capabilities, to address security challenges posed by China.
India has requested some additional S-400 missiles from Russia following the success of the air defense missile system in the recent tension with Pakistan. 

Why India Chose The S-400 ?

• Advanced Technology:- the S-400 is one of the most advances air defense systems globally, this technology is capable of targeting 80 targets simultaneously and engages multiple missiles.
• Regional Security:- The acquisition is driven by India's desire to assert itself regionally and globally, in the context of it's strained relation with China and Pakistan.
• Multi Layered Defense:- India is aiming to create a multi layered defense system, with the S-400 serving as a cornerstone.

India's Indigenous Efforts

• Project Kusha :- India's Defense Research and Development Organization (DRDO) is developing an indigenous long range defense system, set for deployment by 2029.
• Other Initiatives:- DRDO has also developed other notable projects, like Tejas, Agni and Prithvi missile systems, Arjun battle tank and more.

The S-400 missile successfully neutralized swarm of drones unleashed by Pakistan to compensate for the humiliation inflicted by "Operation Sindoor'. 

Key Deal Details

• Deal Value: $5.5 billion for five S-400 Units
• Deployment: Covering borders with China and Pakistan
• Delivery Status: Three Units delivered as of 2024, with the remaining two expected by 2025.

Potential  implications

• It may alter the Strategic Stability
• India is confident of securing a waiver due to it's strategic partnership with the US.