India has begun receiving the fourth squadron of the Russian-made S-400 Triumf air defence system, now referred to as “Sudarshan”, marking a significant boost to the country’s air defence network. Sources said the first batch of the fourth squadron has arrived via the sea route, with deployment expected after the complete system is delivered. The S-400 is part of the $5 billion deal signed with Russia in 2018 for five squadrons. Deliveries of the final two units were delayed due to the Russia-Ukraine war. The fifth squadron is expected to arrive by November. India has already deployed three S-400 squadrons along key western and northern sectors. The Defence Acquisition Council has also approved the procurement of five additional S-400 squadrons following the system’s reported operational performance.