Iran’s support for Ansar Allah (the Houthis) has been a constant worry for the Yemeni state and the Saudis. In RAND’s 2010 report on the Houthis, the authors note that although Iran at this point had started to make some public statements in support of the Houthis, the Iranians were extremely hesitant to enter the fray.
Iranian support for the Houthis seems to have increased since the group has been able to take more territory and governing responsibilities, most notably taking Sanaa, the capital, in September of 2014 and advancing towards Aden
in March of 2015. In an interview with The New York Times, former President Saleh describes the Houthis as “trying to exploit people” by saying that the state is fighting all Zaydis. When asked why Iran supports the Houthis, he had
replied in 2008, “[The Iranians] support them because they think that the rebels are from Ahl al-Bayt [the family of the Prophet Mohammed, of utmost important to Shi‘a]. Just as they support Hassan Nasrallah [leader of Lebanese Hezbollah]. They have this approach. And also to settle scores with the USA. Of course Iran cannot reach the USA so they settle scores with the USA in other countries, whether in Arab nations like Yemen, or otherwise.”