The conflict in Yemen took a dramatic turn in November 2017 when Houthi fighters launched a Burqan 2H long-range missile targeting Riyadh, the Saudi Arabian capital. The missile was intercepted before it could reach its target, but the Saudis, accusing Iran of supplying missiles to the Houthis, termed the attack an “act of war” by Iran (Haaretz, November 6, 2017). Nonetheless, the Houthis repeated the tactic in January, firing a ballistic missile, a Qaher2-M, toward Saudi Arabia’s southern province of Narjan (The National, January 12,).
Saudi Arabia has seen several missile attacks from the Houthis in the past, though few have made media headlines. In fact, in 2015, Saudi Arabia’s King Salman had already voiced his concern to then-Secretary of State John Kerry that Houthi Scuds might reach Mecca. That year the United States conducted a stop a search campaign on shipping in the Red Sea to try to prevent Iran from supplying the Houthis with surface-to-air missiles (The Times of Israel, April 13, 2015).
For its part, Iran strongly denies the Saudi allegation that it provides the missiles fired by Houthis (Haaretz, November 12, 2017). But the two countries are fighting a proxy war in Yemen and, Iranian influence is undeniable, though quite what control Iran really exerts over the Houthis is less clear.
Iran backs Yemen’s Houthi rebels, providing them with aid and weapons, including supplying anti-ship cruise and ballistic missiles, according to U.S. Vice Admiral Kevin M Donegan (Gulf News, September 19, 2017). U.S. General Joe Dunford, chairman of Joint Chiefs of Staff, has voiced concerns the Houthis could use the anti-ship cruise missiles to threaten commercial shipping along two crucial waterways—the Strait of Hormuz and the Bab-el Mandab (al Arabiya, June 18, 2017).
Houthi missiles fired at Saudi Arabia in 2015 were, according to reports, Scud-Cs that resembled the Hwasong-6 missiles of North Korea (al Arabiya, August 4, 2015). It could be that missiles from North Korea came into the Houthi’s hands via Iran (Haaretz, January 19, 2017).
In September 2016, it was reported that the Houthis, who had taken control of the Yemeni capital of Sana’a, stole $4.6 billion from the central bank (al Arabiya, September 20, 2016). These funds could have been used to purchase Iranian weapon systems. Under sanctions, Iran would be keen to provide weapon systems to the Houthis through the black market for cash.
However, Iran is not the only foreign influence on the Houthis. Farea al-Muslimi, a Yemen-based expert on the crisis, has suggested that “countries like Oman and Russia currently have more direct leverage over the Houthis than Iran does.” 
An economic slowdown in Oman has seen it commence trade with Iran and become a strategic ally. Although Muscat denies it, Oman is the most likely transit point for Iranian weapons, which have continued to reach the Houthis despite port blockades and airport closure (The New Arab, October 20; The New Arab, December 20).
Despite being part of the Gulf Cooperating Countries (GCC), Oman has recently chosen to act as a mediator in the Yemen crisis. Even though it is part of the Saudi-led alliance in Yemen, in early 2018 it issued a joint statement with Iran calling on Saudi Arabia to cease its Yemen offensive (AMN, January 9).
Moscow, meanwhile, would like to ensure a ceasefire in Yemen. It likely believes that such a move can enable Russia to gain influence in Yemen and help it establish a naval base in the country that will allow it some control over the Bab-el Mandeb Strait (Middle East Monitor, June 3, 2017).
In July 2017, Yemen’s President Abdrabbuh Mansour Hadi appointed Ahmed Salem al-Wahishi as Yemen’s ambassador to Russia, the first since 2011 and the fall from power of former President Ali Abdullah Saleh (Russian International Affairs Council, December 14, 2017). In October 2017, a visit by Saudi’s King Salman to Moscow gave rise to speculation that Russia could step in to influence Saudi to agree an end to the war (Gulf News, October 17, 2017).
Besides the short-term benefit to the Iranian military-industrial complex of supplying the Houthis, gaining an upper hand in Yemen could allow Iran to overcome Saudi influence in the region and tip the balance of power in its favor. Success in Yemen could see an Iranian military presence there, and Iran is already ascendant elsewhere in the region as a result of its successful interventions in Syria and Iraq.
In 2016, the Iranian chief of staff of the armed forces, General Mohammad Hossein Baqeri, clarified Iran’s intentions and desires when he commented that “[i]t may become possible one day to have bases on the shores of Yemen or Syria.”  However, the Houthis have shown little interest in fulfilling Iran’s ambitions for them. In fact, in 2016, the Houthi political council chief Saleh al-Sama explained that “[n]ot one inch of Yemen’s land or waters will be fortified to any foreign country … whether a friend or an enemy.”  President Hadi, on the other hand, has thrown in his lot with the Saudis and has criticized Iranian backing for the Houthis.
But according to Lieutenant General Graeme Lamb, a former UK special forces commander, “Iran’s involvement in Yemen is a part of a wider regional conflict [in the Middle East], one that Tehran hopes to win by overthrowing the old order and replacing it with one where Iran is better placed to dominate the region.” 
The Houthis want to secure the interests of the Shia and the position of the Zaydis, who have been subjected to political and cultural discrimination (al Akhbar, September). Initially, they supported the ousted former President Saleh, but by the end of 2017 Saleh had broken ties with them, swapping sides to support the Saudi-led coalition (al-Jazeera, December 4). When the Houthis learned of this, they killed him (al-Jazeera, December 10).
The Houthis want influence in Yemen’s politics and to that end have formed a national unity government aimed at securing the interests of the Shia Zaydis (Alwaght, December 1, 2016). They wish to manage the country’s domestic affairs and bring development to their war-torn country.
However, neither Iran nor Russia are likely to allow the Houthis full control of Yemen. While Iran is equipping the Houthis with missile systems to defeat Saudi Arabia, it hopes to gain dominance for itself by using the Houthis as a proxy. Russia, meanwhile, has emerged as a powerful player in the Middle East and will also want its share of influence in Yemen. In fact, the Houthis may find that it is only with the support and cooperation of Iran or Russia that they will be able to bring about the development they want and manage Yemen’s domestic affairs effectively.
 Al-Muslimi , Farea “Iran’s Role in Yemen Exaggerated, but Destructive” (May 19, 2017) See: https://tcf.org/content/report/irans-role-yemen-exaggerated-destructive/
 Naveed Ahmad, “Iran’s quest for foreign naval bases” (January 24, 2017) See: https://www.alaraby.co.uk/english/comment/2017/1/24/irans-quest-for-foreign-naval-bases
 “Worth Dozens of Times More Than Nukes: Iran may seek naval bases in Syria and Yemen” (November 27, 2016) See: https://www.haaretz.com/middle-east-news/iran-may-seek-naval-bases-in-syria-chief-of-staff-says-1.5466781
 Graeme Lamb, “The bloody battle in Yemen shows Iran is intent on dominating the Middle East” (September 2, 2016) See: https://www.telegraph.co.uk/news/2016/09/02/the-bloody-battle-in-yemen-shows-iran-is-intent-on-dominion/