National Security Adviser Ajit Doval is expected to discuss the purchase of more S-400 missile systems Indian National Security Adviser Ajit Doval is scheduled to visit Russia this week to discuss defense and security matters, the Times of India reported on Tuesday. Doval is expected to hold talks with senior Russian officials and is likely to discuss the purchase of more S-400 air defense missile systems, according to the report. India currently has three S-400 systems – part of a larger order