Yemen al-Qaeda attack is new blow to stability
Monday morning's suicide bombing of a military parade is the biggest single attack on Yemeni government forces since President Abdrabbuh Mansour Hadi took office in February.
It appears to be a well-planned retaliation by al-Qaeda for the losses it is suffering in the southern province of Abyan.
Witnesses in the capital Sanaa are still stunned as to how a lone bomber, dressed as a soldier, was able to kill nearly 100 troops with an explosive belt hidden under his uniform.
The soldiers, handpicked by their commanders, had just finished rehearsing for Tuesday's planned parade to celebrate the anniversary of Yemen's unification.
The head of national security, a nephew of the previous president, was immediately replaced by presidential decree after the attack.
'Blown to pieces'
Tom Finn, a British journalist living in Yemen, described what he saw at the scene.
"When I arrived, I immediately saw blood that was splattered on the tarmac, pieces of flesh and also hats and shoes of soldiers which had just been blown to pieces. This debris was scattered 40-50m away from where the explosion went off."
A British military explosives expert who asked not to be named said it would appear to be a classic al-Qaeda-type suicide attack by an improvised explosive device.
He said the group has often used a combination of plastic explosives and ball bearings to lethal effect when detonated in a crowded space.
But Yemen, although no stranger to violence, has been largely spared such carnage in its capital in recent months.
Instead, the fighting between government forces, backed by US military advisors, and Islamist militants has centred around the southern province of Abyan, just east of the port of Aden.
Since 12 May, more than 200 people have reportedly been killed. Largely unseen by the rest of the world, artillery shells are crashing into mountainsides, gunmen are firing out of their AK-47s in the sweltering heat of the open desert, while Yemeni air force warplanes carry out air strikes.
Further to the east, in the craggy valleys of the province of Hadramout, a missile fired from a CIA unmanned aerial drone recently killed three militants believed to be linked to al-Qaeda.
So why, three months after its long-serving and unpopular president, Ali Abdullah Saleh, stepped down in the wake of protests triggered by the Arab Spring, is Yemen still at war?
Yemen is complicated.
The country has profound problems that have nothing to do with al-Qaeda - dwindling oil, dwindling water, rising food prices, soaring unemployment, a Shia insurrection in the north, a separatist movement in the south. Corruption and tribal feuds are rife.
But Yemen is also home to what many consider to be al-Qaeda's most dangerous branch - al-Qaeda in the Arabian Peninsula (AQAP) - which, together with its allied tribal militants, has managed to take significant ground from the government in Abyan province, profiting from the chaos engendered by last year's protests, including looting abandoned warehouses full of weapons.
While the rest of the world has only limited interest in AQAP's bid to take and hold ground inside Yemen, it does worry about the group's global ambitions, especially its expertise in bomb-making.
Starting in August 2009, AQAP has now sent several concealed body bombs outside Yemen borders, with only timely intelligence work by the Saudis and others averting mid-air detonations on planes bound for the US.
Al-Qaeda's master bomb-maker, in hiding in Yemen, has long been identified as a Saudi national, Ibrahim al-Asiri, a jihadist so fanatical he sent his own brother Abdullah on a suicide mission to Jeddah with a device intended to assassinate the Saudi head of counter-terrorism, Prince Mohammed bin Nayef.
The device worked, blowing the bomber in half, but it only very lightly injured the prince.
Osama Bin Laden, the former leader of al-Qaeda who was killed in Pakistan a year ago, had mixed views about what the organisation should be doing in Yemen.
The electronic files seized from his compound in Abbottabad reveal he believed Yemen "should be peaceful and kept as a military reserve for the ummah", the global Muslim community.
But Bin Laden was also keen for it to be used as a springboard for further attacks on the US mainland.
In the files, he exhorts his associates to "concentrate on the Yemeni emigrants who come back to visit Yemen and have American visas or citizenship, and would be able to conduct operations inside America, as long as they have not given their promises not to harm America.
"We need to extend and develop our operations in America and not keep it limited to blowing up airplanes."
His words appear to have been only partly heeded, with a small but determined core of mainly Saudi operatives in AQAP working on ways to attack the US.
This is why the US is now exerting great efforts to support and encourage Yemeni government forces in their efforts to dislodge al-Qaeda from Abyan province and its capital, Zinjibar.
The controversial CIA drone strikes, which are deeply unpopular with Yemen's tribes, and which human rights groups charge are tantamount to extrajudicial killings, have already killed several AQAP operatives, as well as its charismatic and influential ideologue, Anwar al-Awlaki.
The US is now in something of a race to find and eliminate the master bomb-maker before he can train up any more like him.
Even in the remote wildernesses of Yemen's Shabwah, Marib and Abyan provinces, where al-Qaeda has established a scattered presence, a fugitive can only hide for so long before somebody, somewhere, phones in a tip-off.
Today's bombing will likely make Washington and Sanaa redouble their efforts to eliminate al-Qaeda from Yemen. It will not be easy.