The al-Houthi rebels are Shia and violently oppose the mostly Sunni government in Sanaa. They operate in the more densely populated northwest, where mountains, like those in Mali, provide some tactical protection from security forces. In addition to physical protection against government offensives, these mountains stretch into Saudi Arabia, enabling the al-Houthi fighters to engage in cross-border smuggling. However, the rebels' proximity to Saudi Arabia has brought with it Saudi military responses. In 2009, the Saudi military entered Yemen to stop the al-Houthis from gaining too much territory.
Despite a mutual interest in containing the al-Houthis, the Saudi and Yemeni governments are nonetheless constrained by their shared border, which limits military movements and operations. Coordination with a foreign military, no matter how friendly, is inefficient, especially in difficult terrain.
While the largest al-Houthi rebel presence is located in Yemen's Saada province, the group has expanded its territory into Amran and Hajja provinces. The expansion has been under way since late 2011, when the Yemeni government was restricted by protests in Sanaa and by a split in the military, which eventually led to former President Ali Abdullah Saleh's ouster. Security forces were therefore unable to devote the necessary resources to block al-Houthi expansion effectively.
One of the reported goals of this expansion was control of the Red Sea port of Midi, which lies beyond the mountains on the coastal plain. Control of this port would enable al-Houthi rebels to access foreign weapons. The rebels reportedly still have a lingering presence in Amran and Hajja provinces, and they maintain their stronghold in the mountains of Saada province.
Al Qaeda in the Arabian Peninsula
Al Qaeda in the Arabian Peninsula militants predominantly are located in the eastern province of Hadramawt. Relatively uninhabited and difficult to secure, this region has many of the defensive benefits of mountainous terrain, even though it is not as elevated as the mountains in the north. As such, the province enjoys a degree of autonomy.
The eastern mountains are composed mostly of flat-topped mountains, with very steep ravines running through them. These flat tops enable Yemeni security forces to position themselves on high ground, where they can move more efficiently along more traversable routes than in other mountain terrain.
But these advantages are offset by some disadvantages. Movement from the high ground to the ravines, where the militants hide in their camps, and to caves down the steep cliffs that border them, is limited to fixed points. Invading forces can only enter and exit these ravines through the points where the edges are less steep; locating these requires knowledge of the local terrain. This specific element of the topography places immense constraints on the freedom of movement for forces fighting the militants.
Throughout 2012, al Qaeda in the Arabian Peninsula militants also expanded their territory, wresting control of several towns in Abyan province. Because the government was preoccupied with protests and with a mutiny within the military — and because the al-Houthi rebels were expanding their area of operations — al Qaeda in the Arabian Peninsula militants seized the opportunity to take control of populated areas. But when Saleh was replaced by President Abd Rabboh Mansour Hadi, Yemeni security forces regained control of these cities with the help of U.S. and Saudi financial, logistical, intelligence and training support. Al Qaeda in the Arabian Peninsula militants are still operating and conducting attacks in the region, but the main hideout of the organization has been pushed back to the mountains in Hadramawt province.
Pressure, Not Elimination
The various internal conflicts plaguing Yemen help facilitate the militants' survival. These conflicts prevent the government from effectively tackling the militant issues with its security apparatus.
Notably, the government has tried to use the presence of multiple militant groups to its advantage by letting al Qaeda in the Arabian Peninsula and al-Houthi militants fight each other in the Saada region. Yemen and Saudi Arabia also have used local clans in eastern Yemen to oppose al Qaeda operations because the government forces are unable to guarantee security there. The fact that Yemen's security forces are unable to project their power within these remote regions is also one of the reasons al Qaeda in the Arabian Peninsula has chosen to base itself in Yemen instead of in Saudi Arabia. Rather than combat Saudi Arabia's superior security apparatus directly, militants can attack the country from across the border and against Saudi government personnel and infrastructure inside Yemen.
Since Saleh left power, Yemeni security forces, including the military and intelligence departments, have been severely divided between the Saleh clan, the U.S.-trained new guard of the military and the old guard, which consists of many Islamist sympathizers. Hadi has tried to balance these forces against each other, but so far he has not been able to fully consolidate his power. He has received support from the United States and Saudi Arabia and, due to the multiple challenges he faces, relies on this external support to respond to Yemen's various threats.
Intensified unmanned aerial vehicle strikes, facilitated by the United States and Saudi Arabia, have helped Hadi combat al Qaeda in the Arabian Peninsula. Such strikes do not eliminate the militant threat, but they do provide a long-range ability to put pressure on militant networks. This pressure can make networks less efficient by causing their members to be more concerned with their lives than with broader strategic goals and with command and control.
But until Hadi is able to consolidate power completely and unite the military and security apparatuses, militants in Yemen will continue to destabilize the country and carve out more autonomy for their respective campaigns.