The secret SEAL team that took down bin Laden

Navy SEALs are known as super fit, super tough - with a little Rambo thrown in. But the SEALs who killed Osama bin Laden operate on a whole different level - literally. They are what is known inside the Pentagon as a "tier-one force," reserved for only the highest-priority targets, like bin Laden or a loose nuclear weapon, reports CBS News national security correspondent David Martin.

Richard Marcinko, now a best-selling author, was the first commander of what came to be called SEAL Team Six, a counter-terrorist force founded in the wake of the 1980 failure to resuce Americans held hostage in Tehran.

"Tier one means they are the force to be called away first," Marcinko said. "It's been 30 years that they've been practicing and doing counter-terrorism missions so you really have a well-oiled machine that you're fielding when you send them out."

Complete coverage: The killing of Osama bin Laden

Howard Wasdin was a member of SEAL Team Six in Somalia in 1993, shot three times in the infamous Black Hawk Down firefight. By then he'd been through the notoriously tough SEAL boot camp, which is about much more than extreme fitness.

"Those classes routinely start with about 130 people and graduate 25. Those 25 that graudated have one thing: mental toughness above the other guys that didn't make it," Wasdin said.

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That was good enough to make a regular SEAL team. After several years of experience there, he volunteered for Team Six.

"A total of 16 of us applied and two were accepted," Wasdin said.

It was snipers from SEAL team six who picked off Somali pirates holding an American ship captain hostage aboard a lifeboat. But SEAL Team Six is not invincible. British aid worker Laura Norgrove accidentally was killed in a SEAL Team Six rescue mission gone wrong in Afghanistan. Every mission balances on a razor's edge between success and failure. SEAL Team Six goes into every one of them the same.

"Stone professionalism. Controlling your emotions," Wasdin said. The difference between being afraid and a warrior is controlling that fear and using it as a tool in accomplishing the mission."

The 40 minutes SEAL Team Six spent on the ground at bin Laden's compound were 30 years in the making.