Yemen has become the latest terrorist sanctuary, and for many of the usual reasons. Endemic corruption causes constant political tensions and unrest. That, and overpopulation, results in Yemen being the poorest Arab country. It wasn't always that way. For centuries, population was a tenth of what it is now, and with the most rainfall in Arabia, Yemen had food. Its location astride the sea lanes to India and Africa brought trade and prosperity. But in the last century, better medicine and public health care methods from the West has seen the population grow to 24 million. The population is increasingly polarized between secular urbanites and religious conservatives out in the countryside.
For most of the last five centuries, the coastal cities were controlled by Turkey, Portugal or Britain. The interior tribes were controlled by no one. When the tribes to the north united to form Saudi Arabia, a temporary agreement on borders was hammered out in 1934. It has been renewed periodically since then. If is isn't, there could be war. Yemen would probably lose, since Saudi Arabia has much more oil, and weapons, and about the same population. Relations between the two countries have always been tense, with Yemen seeing itself as an ancient, and superior, culture, while the Saudis are a bunch of desert bumpkins who got lucky with all that oil. The extent of this animosity could be seen in 1990. When Iraq invaded Kuwait, and seemed poised to take Saudi Arabia as well, the Yemen government openly supported Iraq. The enraged Saudis then expelled 800,000 Yemenis who were working in Saudi Arabia. Workers from South Asia were brought in as replacements. Yemen now has an unemployment rate of nearly 40 percent, and an increasing number of young Yemenis leave, usually illegally, for the West, to find work.
Another catastrophe, especially in the south, is Khat (or Qat). Khat is grown in Yemen, consuming 40 percent of the water supply, and smuggled quickly to Saudi customers each day. Khat is illegal in Saudi Arabia. In Yemen and Somalia, Khat chewing makes guys with guns more surly and trigger happy than they would normally be. Khat must be relatively fresh, or else it loses its effect. Khat gives you more of a buzz than caffeine or nicotine, but less than stronger drugs. In some countries it is legal, but regulated. Many do not consider it a dangerous drug, but Yemenis spend over a billion dollars a year on it, and cultivation of Khat has ruined Yemeni agriculture and caused a worsening water shortage. Khat production has increased over 50 percent in the last five years. There's big money in Khat, and that money buys cooperation from corrupt government officials. So efforts to impose a legal ban on Khat growing have failed. Because of Khat growing, the country is expected to suffer severe water shortages in the next decade or so.
In addition to the economic and political problems, Saudi Arabia has, for decades, been building mosques and religious schools, and paying for clergy to preach and teach. This is most effective among the rural tribes, who are now inclined to provide sanctuary for al Qaeda. These Islamic terrorists actually represent a murderous branch of the conservative Wahhabi form of Islam the dominates in Saudi Arabia, and is popular with rural Yemenis.
Thus Yemen is fertile ground for Islamic terrorists, and that is not likely to change anytime soon.