How Iran and Saudi Arabia's rivalry has plunged the Middle East into sectarian war. FRONTLINE traces how a 40-year rivalry between Iran and Saudi Arabia has fueled sectarian extremism across the Middle East for political gain. Correspondent Martin Smith travels to seven countries, including Iran, Saudi Arabia, Syria, Iraq and Yemen to examine how the power struggle has rippled across the region. This journalism is made possible by viewers like you. Support your local PBS station here: www.pbs.org/donate Love FRONTLINE? Find us on the PBS Video App where there are more than 250 FRONTLINE documentaries available for you to watch any time: to.pbs.org/FLVideoApp Subscribe on YouTube: bit.ly/1BycsJW #BitterRivals #Iran #SaudiArabia Instagram: www.instagram.com/frontlinepbs Twitter: twitter.com/frontlinepbs Facebook: www.facebook.com/frontline FRONTLINE is streaming more than 200 documentaries online, for free, here: to.pbs.org/hxRvQP Funding for FRONTLINE is provided through the support of PBS viewers and by the Corporation for Public Broadcasting. Major funding for FRONTLINE is provided by the John D. and Catherine T. MacArthur Foundation and the Ford Foundation. Additional funding is provided by The John and Helen Glessner Family Trust, the Park Foundation, and the FRONTLINE Journalism Fund with major support from Jon and Jo Ann Hagler on behalf of the Jon L. Hagler Foundation. Major support "Bitter Rivals: Iran and Saudi Arabia" is provided by the Corporation for Public Broadcasting. Additional funding for this program is provided by the Henry Luce Foundation and the Pew Charitable Trusts.