In the tangled mythology of the Greeks, the Hydra was a hideous serpent that guarded one of the entrances to the underworld. The creature possessed several heads (dozens or hundreds, depending on the source) and whenever one was cut off, two grew back in its place.
The modern woes of the Arabian Peninsula's oldest country can seem as intractable as the Greek serpent. With so many challenges facing Yemen, policymakers can struggle to understand, let alone advance, the country.
The arrival this week in Sana'a of Washington's top foreign envoy is a clear indication that Yemen is moving up the US political agenda. Hillary Clinton spoke of the threat al Qa'eda poses to both the United States and Yemen and said the partnership between the two countries would be a long-term one.
It is true that al Qa'eda in Yemen is a serious concern for the United States. US wars have scattered the group's original base and jihadists have settled in the lands of Somalia and some regions of Yemen.
A US-born preacher of Yemeni descent, Anwar al Awlaki, is at the forefront of Mrs Clinton's mind. Mr al Awlaki, a purveyor of fiery internet sermons, has been linked to several attempted attacks on westerners, including the Nigerian "underwear" bomber, Umar Farouk Abdulmuttalab, and Faisal Shahzad, a Pakistani-American who planted a bomb in New York's Times Square that mercifully failed to explode. Of greatest concern are the bombs inside printer cartridges that were sent as air cargo from Yemen in October.
Although these attacks lacked the scale and planning of 9/11, there are two elements that frighten the United States: first, that those attacks fell through holes in international security. It was only by luck that the bombs in New York or above Detroit failed to explode. Even the cartridge bombs were already in the air and were found only because of intelligence from Saudi Arabia.
Second, Mr al Awlaki is still preaching and may be radicalising others around the world. Last summer, a British student at a prestigious university stabbed a parliamentarian. Previously unknown to the police, 21-year-old Roshanara Choudhry said she decided to kill the MP after hearing Mr al Awlaki's sermons. Crucially, her radicalisation occurred in a matter of months, alone in her room. If Mr al Awlaki's sermons, freely available on the internet, could provoke such a change, the questions are, who else has he influenced, and where are they?
Al Qa'eda, or at least a terrorist group using the moniker al Qa'eda in the Arabian Peninsula, is also a threat to Yemen itself. Its attacks within the country have killed more than its attacks abroad.
Yet al Qa'eda is a comparatively low priority for Yemen's government; the peninsula's first democracy faces even more serious challenges from within.
Talk of the country's collapse is exaggerated. The economy is growing, albeit slowly; in July, the World Bank reclassified Yemen as a middle-income country. Political and economic reforms are being enacted: steps agreed a year ago in London, when an international conference brought together the G8, the GCC and other important Middle Eastern players such as Turkey and Egypt, are being carried out. And the country's international profile is being raised: the successful hosting of this past winter's Gulf Cup showed that security issues are manageable.
Yet Yemen's challenges are still immense. The government in Sana'a remains dependent for funds on limited oil supplies. Unless new fields are discovered, Yemen's oil could run out by the end of the decade, a serious problem given that it now accounts for 75 per cent of government revenues. The broader economy is facing significant difficulties. Inflation remains a problem and foreign investment is down - a combination of security jitters and the global downturn.
With limited financial resources from oil, the state is growing weaker across vast areas of the country. In the north, the writ of the government already runs weak. What is usually called the Houthi rebellion in the Sa'ada province bordering Saudi Arabia has displaced a quarter of a million people. Despite a ceasefire in February last year, there has been sporadic fighting.
A greater issue for the president, Ali Abdullah Saleh, is the secession movement in the south. With fewer people, most of the oil and much of the country's land, southerners increasingly feel they have done badly out of unity. For the past three years, southern Yemenis have been holding protests calling for a fairer share of national wealth and civil service positions.
Both of those conflicts are more complex and far-ranging than the few hundred jihadists running around in the eastern deserts, and more likely to unsettle the country. Add a looming water crisis (the UN Food and Agriculture Organisation lists Yemen among the most water-scarce countries of the world) and that the country is on the front line for migrants out of Africa, with many drowning before they make it to Yemen's southern beaches, and you have a potent cocktail.
These are the Hydra heads Yemen faces, and slaying them will not be easy. Yet, as Mrs Clinton pointed out, the cost of doing nothing will be high. Sitting on the Gulf of Aden, Yemen is strategically important to the region.
What can be done, and at what cost? US aid to Yemen topped US$300 million (Dh1.1 billion) last year and, as leaked diplomatic cables showed, military co-operation has expanded. Yet such sums, though significant, pale in comparison with the hundreds of millions of dollars pumped into stabilising Pakistan or Afghanistan. Abu Bakr al Qirbi, Yemen's foreign minister, has said the country may need as much as $4bn.
Aid can help, but more creative solutions are needed, especially from Yemen's Gulf neighbours. Saudi Arabia, Oman, Qatar and the UAE stand to benefit from a stable and prosperous neighbour. The Gulf states also have an added weapon: rich Yemenis, with family links and a stake in future prosperity.
What is needed, first, are stronger "soft" links between the Gulf and Yemen, through training, education and exchanges. Yemenis and other Arabs can provide funds for scholarships, particularly in technical qualifications and the sciences, with the stipulation that beneficiaries return to work in Yemen for a set period of time. Planning for a post-oil economy has to begin. Microfinancing enterprises are also essential to restart the economy, in tandem with legal safeguards for new businesses. Neighbours can provide the funds for the former, and the push for the latter.
The long-term goal ought to be to tie Yemen into the economy of the GCC. With 24 million people, and a common language and culture, Yemen has the human resources many of the Gulf states need.
In Greek mythology, a penitent Heracles needed outside help to defeat the Hydra. It will take more than one visit from Mrs Clinton's Iolaus to help Yemen tame the many heads of its Hydra.
Faisal al Yafai received the 2010 Ibn Battuta Award for Journalism