China has deployed its S-400 missile defence system on the Indian border. The S-400 missiles are the strongest and the most effective missile defence system at present. It has been currently deployed along the Line of Actual Control by China. This is the latest movement on the Chinese side in a series of escalations as the tension between India and China escalates. Russia had sold the S-400 system to China in 2018. China already owns the S-300 missile system too.