Yemen is just another facet in the Iranian/KSA conflict or better stated Sunni/Shia hegemony of the Muslim global community which started under Khomeini and continues under Khamenei......while there is no common Shia/Sunni border in Syria to KSA...THERE is one between Yemen and KSA....
AND there has been continuous Iranian attempts to rile up the Shia minority inside KSA....along with IS which has Iranian backing as well...

Map of #Saudi, #UAE, & insurgent spheres of influence inside #Yemen, via @nytimes & @AEIfdp:
http://www.nytimes.com/2016/10/14/wo...mtyp=cur&_r=0#
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