Just weeks before his death on January 3, Colonel-General Igor Sergun, director of Russia's GRU military intelligence agency, was sent to Damascus on a delicate mission.

The general, who is believed to have cut his teeth as a Soviet operative in Syria, bore a message from Vladimir Putin for President Bashar al-Assad: the Kremlin, the Syrian dictator's most powerful international protector, believed it was time for him to step aside.