Members of the Shiite Houthi group gather near the northern town of Hamdanon after rebel commander Abdulmalik al-Houthi called his followers to march on the Yemeni capital Sana'a, August 19, 2014. (Amal Noman/AFP/Getty Images)

Members of the Shiite Houthi group gather near the northern town of Hamdanon after rebel commander Abdulmalik al-Houthi called his followers to march on the Yemeni capital Sana'a, August 19, 2014. (Amal Noman/AFP/Getty Images)

Yemen is facing one of the greatest periods of instability since it emerged from the Arab Spring uprisings. The Houthis have seized the capital, Sana’a, and President Abdu Rabbu Mansour Hadi and Prime Minister Khaled Bahah stepped down after being put under de facto house arrest by the rebels. As they did last September—when the Houthis first took over Sana’a—the Zaydi Shia’a rebels negotiated a withdrawal but then refused to abide by their side of the deal.

The Houthis now effectively control the capital as well as significant swaths of northern Yemen, which they tightened their grasp on during and shortly after the Arab Spring uprising. The group now appears to be moving to take over key oil and gas fields and pipelines leading to the Gulf of Aden and Red Sea export terminals. It remains too early to say what the Houthis want or how they will respond to suddenly owning—rather than merely intimidating—the halls of power. It is worth considering how Yemen got to this point. Below I lay out three factors which, while not all-encompassing, were particularly important.

First, the country has been without an effective and cohesive security apparatus for three and a half years. The army, most notably, fragmented during the Arab Spring uprisings with particular commanders aligning themselves with the demonstrators and others backing then-president Ali Abdullah Saleh. The fracturing of the security services was, at least in 2011, useful in generating a stalemate (a “balance of weakness,” as it has been labeled) that pushed key figures into UN-facilitated negotiations. However, sine 2012, the absence of robust security services has only served to undermine the country and allow myriad armed groups to flourish. Read more