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Virtually powerless for months, Yemen's embattled President Abed Rabbo Mansour Hadi looked ready to leave the country after fleeing Shiite rebels who seized the capital in September and held him captive in his own home for weeks.

But the soft-spoken technocrat who has long avoided the limelight stepped straight into it on Saturday, renouncing his own resignation and challenging the Shiite Houthi rebels who hold large parts of the country.

Hadi's sudden resurgence after years of quiet rule raises fears that Yemen, the Arab world's poorest country, only united in the 1990s, will fracture into mini-states, complicating American efforts to combat al-Qaida's powerful local franchise.

"He's usually very passive and placid, so such a strong statement took a lot of people by surprise — Hadi basically drew the battle lines," said Yemeni political analyst Hisham al-Omeisy. "A lot of people are actually doubting the statement, saying it's too strong for the Hadi we know, and want to see him read it on TV before they believe it," he added.

Before Saturday, the 69-year-old Hadi largely kept to himself, running the country of 24 million people while making few public comments or speeches. Hadi studied at a string of military institutes in the now-defunct South Yemen, which had been the Arab world's only Marxist country in the years after Britain withdrew in 1967.

After a ruinous civil war with the north, Hadi rose to the rank of major general in the unified Yemeni army. In 1994, he was appointed vice president under President Ali Abdullah Saleh, a Machiavellian autocrat who deftly manipulated and managed the fractured country's tribal and regional rivalries during his three-decade rule.

After Yemen's 2011 Arab Spring revolt, Saleh reluctantly handed power to Hadi the following year in a deal brokered by Yemen's powerful Gulf neighbors and backed by the United States. Saleh received immunity from prosecution and remained in Yemen.

Hadi soon found himself atop a government with many hidden enemies and few true allies. He faced a protracted struggle with militants from al-Qaida in the Arabian Peninsula, considered by Washington to be the world's most dangerous branch of the terror group due to its failed attacks on the American homeland. Hadi also faced a simmering separatist movement in the south and increasingly aggressive Shiite Houthi rebels in the north.

"He lacked a strong power base, having left the south long ago, and had little influence with the northern tribes that are historically the most potent force in the country, militarily and politically," said Washington-based Yemen analyst Michael Horton.

But Hadi quickly proved a willing ally to the United States in its campaign of drone strikes on the country's local al-Qaida branch, which claimed responsibility for last month's attack on the French satirical magazine Charlie Hebdo. After Hadi came to power in 2012, the number of suspected U.S. strikes nearly quadrupled, with 56 in 2012 alone, according to the New America Foundation's International Security Program, which tracks the American campaign.

The Yemeni army, bolstered by the strikes, drove al-Qaida fighters out of several towns and cities in the south. Yemeni intelligence officials say hundreds of radicalized foreigners, including Europeans, remain at large today in rural parts of the south.

But the U.S. drone strikes also killed civilians, and as images of the dead circulated in Yemeni media, many began to dismiss Hadi as an American stooge.

His problems only worsened as he tried to reform Yemen's security services, dismissing Saleh's relatives and backers from key positions. When Hadi stripped Saleh's son of his command of the Republican Guard in August 2012, hundreds from the elite military unit encircled the Defense Ministry and tried to force their way inside, starting a shootout that killed five people.

Last year the Houthis, Zayidi Shiites allegedly backed by Iran, emerged as Hadi's gravest threat. Many accused Saleh, himself a Zayidi, of encouraging the Houthis' increasingly bold attacks on government strongholds, a charge he denied despite suspicions that Saleh loyalists in Yemen's military were aiding the Houthis' swift gains.

When the Houthis invaded Sanaa in September, Saleh openly sided with them. The United Nations Security Council imposed sanctions on Saleh for threatening the country's security and stability. His party responded by rejecting a new U.N.-brokered coalition government led by Hadi.

The Houthis surrounded Hadi's home in January and the president soon tendered his resignation, though Yemen's parliament never accepted it as required by law. The Houthis later dissolved parliament and on Saturday Hadi fled to Aden.

On Sunday, Hadi's office said in a statement that he "exercises his functions as president of the republic in Aden with legitimacy not subject to questioning," again raising the stakes.

"The situation has been deteriorating over the past few months from worse to a tyranny, basically," al-Omeisy said. "If Hadi actually means what he said, it is inevitably going to lead to some sort of a war between Hadi and the Houthis."

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