Yemen crisis: First things to know

Fears of sectarian violence in Yemen were heightened on Friday after suicide attacks on two Shiite mosques in the capital, Sanaa, which killed at least 130 people and left more than 300 wounded. Both of the mosques serve members of the country’s minority Zaidi Shiite sect, which is followed by the Houthi rebel movement that has recently become the most powerful force in the country. Recent months have seen increasing violence by Sunni extremists against Shiite supporters of the Houthis, who forced Yemeni President Abd-Rabbu Mansour Hadi to step down in January after seizing the capital.

The Houthis, also known as Ansar Allah (Partisans of God), have long complained of being marginalized in the majority-Sunni country. Nearly one-third of Yemen’s population also belongs to their Zaidi sect of Shi’ism, whose traditions Houthis have attempted to protect in the face of threats by Sunni militants.

The group takes its name from Hussein Badr al-Din al-Houthi, who led the group’s first uprising in 2004 in an attempt to gain greater autonomy for the northern Saada province from which the group hails. Following Houthi’s killing at the hands of the Yemeni military in late 2004, members of his family took control of the group, leading five more rebellions before signing a ceasefire with the government in 2010.

When Yemen’s anti-government demonstrations began during the Arab Spring in 2011, the Houthis joined the protest movement against then-President Ali Abdallah Saleh, capitalizing on the government’s instability to expand their power in Saada and the neighboring Amran province.

From this position of strength, the group’s current leader Abdul Malik al-Houthi demanded in August that President Hadi cancel proposed subsidy cuts, in a call that was supported by thousands of Houthi protesters who began sit-ins around government buildings in Sanaa. The protests turned violent after security forces opened fire on protesters, prompting Houthi rebels to seize parts of the capital in September.

Over the following months, the rebels tightened their grip on the capital, culminating in the seizure of the presidential palace in January. Hadi was put under house arrest but later fled to the southern city of Aden, where he declared himself to be President still.

Hadi, who was elected in 2012, is largely supported by the international community. Hadi’s supporters are not the only ones who have opposed the Houthis. One of the group’s biggest rivals in the country is al Qaeda in the Arabian Peninsula, one of the global jihadist movement’s most dangerous affiliates.

While the Houthi movement has primarily focused its energies on challenging Yemen’s central government, it has also increasingly confronted AQAP (Al-Qaeda in the Arabian Peninsula), even expanding its campaign against the Sunni jihadists in parts of the center and south of Yemen. AQAP has vowed to attack Houthi loyalists across the country. The escalating confrontation between the Shiite Houthis and the Sunni al-Qaeda extremists has raised fears that Yemen’s security crisis could become a sectarian conflict.

Saudi Arabia, Iran’s most significant regional rival, is staunchly opposed to the Houthis, which it deems a terrorist organization. The oil-rich kingdom shares a 1,000 mile-long border (1,600 km) with Yemen. The prospect of a Shiite-controlled state just adjacent to its southern border region is "obviously" something the Saudis fear.

US policy is to cling on to the legitimacy of the presidency of President Hadi, because he was genuinely elected by his people. The U.S. position is also to cling to the national dialogue, the negotiations that have been going on between various factions of Yemen led by a United Nations envoy.