THE last American troops have been pulled out of Yemen after al-Qaeda fighters stormed a city near their base recently. Houthi rebels who had already overrun most of the country have now entered Aden, the last stronghold of President Abdrabbuh Mansour Hadi. And last Wednesday Hadi boarded a helicopter and
Bitter, four-way struggle for control of strife-torn Yemen
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Angry at the status the north was being offered in a proposed new federal constitution, the Houthis came south in force and seized Sanaa last September. In February, after months of house arrest, Hadi fled to the southern port of Aden, his home town and Yemen's second city, and declared it the capital instead. So the Houthis came after him.
Meanwhile Saleh, the former president, returned from exile and made an alliance with the Houthis - despite the fact that he had launched six major offensives against them back when he was president.
The third contender for power is al-Qaeda in the Arabian Peninsula (AQAP), whose forces are only a half-hour's drive from Aden. As its fighters closed in on Aden, AQAP seized the town next to the airbase where the US forces were living, and Washington ordered its troops out.
But the Houthis got into the city of Aden first, and it is not yet clear whether AQAP will try to take it from them.
Finally, we mustn't forget the fighters of Isis (Islamic State), who announced their presence in the country last month. Their sole operation of note so far has been suicide attacks on two Shia mosques in Sanaa that killed 137 people. But as Sunni fanatics in a country that is being overrun by its Shia minority, Isis will not lack for recruits.
In conventional terms, Yemen doesn't matter much. It has a lot of people (25 million), but it is the poorest country in the Arab world. Its oil has almost run out and its water is going fast. You could argue its geographical position is "strategic" - commanding the approach to the Suez Canal - but it's hard to see any Yemeni Government getting the kind of military forces it would need to close that waterway.
What worries people is the possibility that the jihadis (either al-Qaeda or Isis) could come out of this on top. They are certainly not there yet, but many Sunnis will see them as the best chance to break the hold of the Shias who, despite their internal quarrels, have collectively dominated the country for so long. In fact, al-Qaeda and Isis are now the last organised Sunni forces facing the Houthis.
Shias are only one-third of Yemen's population and the resentment runs deep. The Houthi troops now occupy almost three-quarters of the country's densely populated areas, but they are spread very thinly, and if they start to lose they could be rolled up very quickly by the jihadis.
That could turn Yemen into a terrorist-ruled "Islamic State" with five times the population of the one that sprang into existence last July on the Syrian-Iraqi border. The odds are against it, but nobody is ruling it out.
-Gwynne Dyer is an independent journalist whose articles are published in 45 countries