Navy Seals: Tough, all-action heroes who operate at highest level in a shadowy world

Officially, there is no Navy Seals Team Six.

Recruits to this team of elite US commandos are supposed to play dumb if cornered and questioned on its operations. It is no secret that a "best of the best" team has long existed for special operations such as the raid on Osama Bin Laden's compound this year and former members have written books and given interviews about its secretive world.

In the US, the unit has been compared to comic book superheroes. The New York Times hailed them as "America's Jedi Knights" after Bin Laden's death was confirmed. But training superheroes does not come cheap. It is estimated that $1m may have been spent on training every commando who makes the grade.

The team's legend is built around a gruelling initiation programme which sees hundreds of hopefuls quit without even getting to see a sniper rifle. All inductees must be able to complete 100 push-ups against a two minute stop-clock – by all accounts one of the simpler tests. At least six months of physical and mental tests are designed to root out the weak, those who, tired and hungry, reach for a brass bell to ring. That's the signal they want to pull out and go home.

"Hell Week", midway through the training, is famous among the US armed forces. In this part of the Seals' recruitment process applicants are permitted just four hours' sleep in five days. The rest of the time they run, swim in freezing water and take on physical challenges for 20 hours a day. Howard Wasdin, a former team sixer who wrote about his experiences, said: "We would have our hands tied behind our back, feet bound, and be thrown into the swimming pool. Most people are going to freak out over that, but that is just one way we were taught to control our fear, control our emotion, keep your heart rate down, relax and concentrate on what you're doing right now."

If they pass all of the challenges – and the final team is thought to number only 200 at any one time – recruits are expected to learn foreign languages and qualify as battlefield surgeons capable of high- pressure medical treatment.

President Kennedy ordered the creation of the first two Navy Seals teams in 1962 and later they embarked on secret missions during the Vietnam War. Team Six came together formally in the aftermath of failed attempts to rescue American hostages in Iran in 1980. Operatives are understood to have since worked in Bosnia, Somalia, and Rwanda, and have targeting terrorists in Iraq and Afghanistan. Its operations are meant to be kept highly confidential; even its name was chosen to create mystery. Enemy forces might be frightened at the prospect of there being at least six special Seals units when in fact there were only three.