India and Russia signed an over Rs 35,000 crore deal for five squadrons of S-400. The Indian Air Force, which recently received the indigenous MR-SAM and Akash missile systems as well as the Israeli Spyder quick reaction surface-to-air missile systems, believes the S-400 will be a game changer for it. The Sudarshan S-400 air defence missile system achieved a major success in a recent exercise where it ‘shot down’ 80 per cent of the ‘enemy’ fighter aircraft package while forcing others to retreat, aborting their missions. The Indian Air Force has significantly improved its air defence capabilities in recent years.Air defence systems have been deployed in a big way by the Chinese military across the Line of Actual Control, while India has also deployed its own systems in a big way there. Between Patriot missile system and S-400 which system has proven to be more effective in the battlefield ?