Long shot ... The US special forces attempt to rescue two Western hostages in Yemen at the weekend was up agains the odds from the outset. Source: US Defence Source: Supplied

It’s all about the element of surprise.

The commandos want to be the surprise. They don’t want it dished out at them.

But that’s what’s happened on no less than three recent high-profile US special forces raids.

It’s a humbling reminder of the limitations of high technology, and the influence of lady luck.

Despite the enormous power of satellite and drone surveillance, and an extensive internet and telecommunications spy program, the ‘best-of-the-best’ have been foiled by some of the most basic possible precautions.

The weekend’s raid on Yemen appears to be a case in point.

Dark purpose ... A V-22 Osprey combat transport aircraft sits on the deck of a US amphibious assault ship. These aircraft carried US Navy SEALS on the weekend raid. Source: US Defence Source: Supplied

Element of surprise

The ominous-looking CV-22 Osprey combat transport ‘tilt-rotor’ aircraft raced low over the sea before lifting above the rugged Yemen coastline.

The dull grey aircraft did not go unnoticed as they flashed overhead carrying the more than 40 members of SEAL team Six at more than 500km/h. Tribesmen saw them fly above Wadi Abdan in Shabwa province.

They were used to the presence of US drones. This was different.

For the US forces, it was always going to be risky.

The element of surprise had already been lost.

A similar attempt by SEALs to conduct a rescue last month from a jihadist hide-out failed to locate their key targets as the Western hostages weren’t where they were supposed to be. Eight others, however, were released.

But the raid had alerted the al-Qaeda in the Arabian Peninsula (AQAP) operatives that the US meant business. They knew there’d likely be a follow-up attempt to rescue US freelance photographer Luke Somers and South African teacher Pierre Korkie.

This time, they’d be ready.

Now the success of the US operation hinged on just two tactical imperatives:

Speed: Get in fast. Get it done fast before the enemy can react. Get out fast. If a Special Forces objective isn’t achieved in the first few minutes, it isn’t likely to be achieved at all.

Purpose: A clear goal, something that every solder knows and understands — and is committed to achieve.

Even these imperatives were challenged: It was now also a rushed operation.

Hostage Luke Somers, 33, an American photojournalist who was kidnapped over a year ago by al-Qaeda. Source: AP Source: AP

Hostage Pierre Korkie, a South African teacher held by al-Qaeda militants in Yemen. Source: AP Source: AP

Precipitous advance

Plans had to be hurriedly brought forward after AQAP suddenly declared through an online video that it would be executing Somers on Saturday.

“It’s now been well over a year since I’ve been kidnapped,” Somers was seen to say. “I’m certain that my life is in danger. So as I sit here now, I ask, if anything can be done, please let it be done.”

His captors gave the US just three days to meet their demands.

The US commandos had to act: They had little to lose (other than their own lives), but they also had little margin for error.

“Luke’s life was in imminent danger,” the US Commander-in-Chief, President Barack Obama, said in statement. “Based on this assessment, and as soon as there was reliable intelligence and an operational plan, I authorised a rescue attempt.”

Dogged resolve ... A Navy SEAL platoon as they perform a land warfare demonstration with a combat dog. A dog’s bark is said to have exposed their presence in the recent raid in Yemen. Source: AFP Source: News Limited

Odds against them

Despite the high-profile success of the commando raid which killed al-Qaeda kingpin Osama bin Laden in 2011, such operations have recently met with little success.

RELATED: The mission to save James Foley

A July raid against the Islamic State also failed to secure a hostage: Then it was James Foley. Despite the best-laid plans, the attack on a moonless night went awry simply because the jihadists had been following a policy of frequently moving their captives. The facility was overwhelmed by the commandos, but found to be empty.

RELATED: The mission to strike at al-Shabab’s heart

An attack on Somalia late last year — intended to capture or kill key terrorist leaders — was also foiled by bad luck. SEAL commandos were spotted as they moved into position around their target. The ensuing firefight, close to a civilian centre, forced the US troops to withdraw empty-handed.

Mission impossible ... V-22 Osprey tilt rotor aircraft during night operations. Source: AP Source: AP

Floating fortress ... The USS Makin Island (LHD-8) was the amphibious assault ship which acted as the mobile base for the raid on the Yemen branch of al-Qaeda. Source: FACEBOOK Source: Facebook

Combat drop

Our picture of what happened at the weekend is patchy. But enough has been leaked by “officials close to the source” to US media for a sketched outline.

We know the SEALs had been aboard the USS Makin Island, a troop and helicopter carrying assault ship, lingering off the coast of Yemen for just such an opportunity for some time.

We know the Ospreys can carry between 24 and 32 troops each. We know ‘backup’ aircraft are included in case something goes wrong.

Their target was a remote compound in rugged, mountainous terrain in the Shabwah Governate, buried deep in central Yemen.

It would likely have been the subject of secret surveillance — either by drone or otherwise — for days prior. The location of every pebble would have been noted. Exact numbers of people counted. Floorplans drawn up.

“This was difficult terrain to get to and a well-defended compound,” a defence official told reporters.

For this reason, the SEALS had to arrive unannounced.

To that end, they were dropped off in a gully some 10 kilometres from their target at 1am — well outside of earshot of the Ospreys’ whirling engines. It was then a forced march over rugged terrain under a dark sky, guided by their Yemeni allies and night-vision goggles.

Creatures of the night ... Special Operations Forces and US soldiers are shown here conducting a joint search and rescue mission at an undisclosed location in Iraq. Source: AFP Source: News Limited

Alert, not alarmed

The most critical part of the mission was the first five minutes after the firefight broke out.

The commandos planned to be in and out within 30 minutes.

But they were not fast enough against a prepared enemy.

Nor were they lucky.

Bloomberg and the Wall Street Journal report the silent arrival of the US Navy SEALS was announced by a barking dog while the commandos were still some 90 metres from - and attempting to encircle - their objective. US ABC News says the soldiers were spotted by an al-Qaeda operative while “relieving himself”

They could not reach their objective in time: With al-Qaeda alerted, the SEALS had to fight their way through a string of subdivided compounds.

That would take time.

Some reports say a man was seen running into the building believed to contain the hostages. Either way, al-Qaeda fighters appear to have shot both captives in the opening moments of the firefight.

“When the element of surprise was lost, we believe that is when they were murdered,” a defence official told US media. “They were shot nearly immediately.”

Safe haven ... The USS Makin Island (LHD-8), a Wasp-class amphibious assault ship. Source: FACEBOOK Source: Facebook

Evacuation

The first commandos on the scene discovered both hostages were still alive, though in critical conditions.

“There is zero possibility that the hostages were victims of crossfire,” a military official told US media. “This was an execution.”

As combat medics attempted to stabilise the two hostages, an evacuation Osprey was hurriedly called in.

The firefight was reportedly still under way.

One man, believed to be Korkie, lost his fight for life while being raced back to hospital facilities aboard the USS Makin Island. Somers is believed to have been pronounced dead after arriving aboard the ship.

None of the SEALs were injured, though four Yemeni counterterrorism troops were.

Six al-Qaeda militants were said to have been killed.