How the S-400 deal will boost India’s air defence and why is the US unhappy

India is expected to receive the first batch of S-400 air defence systems from Russia by the end of 2021. Russia will deliver the air defence missile systems to India under a $5.4 billion deal. S-400 was developed in the 1990s by Russia as an upgrade to the S-300 series of surface-to-surface air missile systems. However, the US is unhappy with the deal and had threatened India with sanctions during the previous Trump era. The United States has already slapped sanctions on China and Turkey for military deals with Russia. Watch the full video for more. Watch the full video for more.