India's decision to choose the S-400 air defence system over the American THAAD (Terminal High Altitude Area Defence) system was influenced by several strategic, operational, and economic factors.

On October 15, 2016, during the BRICS Summit, India signed an Inter-governmental Agreement with Russia for the procurement of five S-400 regiments, formalizing a deal worth approximately $5.43 billion on October 5, 2018. This decision came despite significant pressure from the United States, which threatened sanctions under the Countering America’s Adversaries Through Sanctions Act (CAATSA) if India proceeded with the purchase.

Key Reasons For Choosing S-400

Versatility and Capability

The S-400 system is renowned for its versatility. It can engage a wide range of aerial threats, including aircraft, drones, and ballistic missiles, at various altitudes and ranges. It employs multiple missile types, allowing it to cover targets from 40 km to 400 km away. In contrast, THAAD is primarily designed to intercept ballistic missiles during their terminal phase and lacks the comprehensive engagement capabilities of the S-400.

2. Compatibility With Existing Systems

The S-400 is highly compatible with India's existing air defence infrastructure, including systems like the S-125 and aircraft such as the Su-30MKI. This interoperability enhances India's overall defence capabilities without requiring significant changes to its current military hardware.

Cost Considerations

The S-400 is less expensive than THAAD. Each S-400 system costs about $550 million and includes multiple launchers and missiles, while a THAAD system costs around $900 million with fewer interceptors. This cost efficiency allows India to deploy more units for wider coverage.

Strategic Defence Needs

Given India's geopolitical challenges, particularly with neighbouring countries like Pakistan and China, the S-400's ability to engage targets deep within enemy territory is crucial. The THAAD system's limited range means it would require multiple units to cover similar areas, making it less effective for India's needs.

India's choice of the S-400 over THAAD reflects a strategic decision aimed at enhancing its air defence capabilities while considering operational effectiveness, cost efficiency, and compatibility with existing systems. Despite U.S. warnings and potential sanctions, India has prioritized its defence requirements and regional security dynamics in this significant acquisition decision.