President Ali Abdullah Saleh, who has ruled Yemen since 1978, stepped down from power on Monday under strong domestic and international pressure. He became the fourth Arab leader ousted since the dawn of the so-called Arab Spring last year.

Saleh was succeeded by his longtime crony Abed Rabu Mansour Hadi, an army field marshal who served as his vice president. Hadi, who represents continuity much more than genuine change, now faces enormous challenges in stabilizing Yemen, one of the poorest and most turbulent Arab countries. The new government is confronted with continued demands for reform from civil society groups, a factionalized army, the persistent Houthi rebellion in the north, rising demands for secession in the south, and the growing threat of al-Qaeda in the Arabian Peninsula (AQAP).

Although Saleh stepped down, much of his regime remains in power. Many in the opposition fear that Hadi will merely serve as an extension of Saleh’s rule. After all, Saleh’s family members still control key government posts, including those in the security forces responsible for crackdowns on the opposition.

Beyond Yemen’s volatile political dynamics exists an escalating security crisis. Last year, when Saleh’s attention was focused more on shooting protestors than terrorists, al-Qaeda took advantage of the power vacuum. In May 2011, Ansar al-Sharia, an al-Qaeda-linked group, occupied the southern town of Zinjibar. A strategically important port, Zinjibar is located east of the Bab al-Mandab Strait, through which 3 million barrels of oil is exported per day. Last month, al-Qaeda made further advances when it captured Radda, a town just 100 miles south of Sana’a, the capital.

The United States, which cooperated with Saudi Arabia to pressure Saleh to step down, hopes that the new government will become a more effective partner in fighting AQAP and other hostile Islamist movements. Although the Yemeni government cooperated in the hunt for AQAP leader Anwar Al-Awlaki, who was killed in a drone strike last September, it has been too busy fighting for its own survival to focus effectively on AQAP in recent months.

President Hadi’s transitional government has pledged to conduct a national dialogue in preparation for an election for a new government in 2014. The United States has a major stake in helping his regime pull Yemen back from the brink of civil war, to deny al-Qaeda an opportunity to exploit the growing anarchy created by the popular rebellion against the unpopular Saleh regime.