Business Insider:
Saudi Arabia agreed to purchase Russia’s advanced S-400 Triumf missile-defense system on Thursday during King Salman’s visit to Moscow.
The agreement marked the second time in the last month that a US ally has agreed to purchase the S-400 system from Moscow.
In September, Turkey finalized and made a deposit on a $2.5 billion deal for the S-400, deepening tensions between Washington and Ankara…