Navy SEALs are involved in the most treacherous and secretive military operations. An assignment might require SEALs to surprise an enemy by swimming silently ashore from a submarine in darkness, or to rappel from a helicopter onto a mountain peak.

The yearlong training program in Coronado, Calif., outside San Diego is most intense during Hell Week, a cold, wet, gritty stretch of almost constant exertion that is designed to make candidates quit. The men are on the run around the clock, getting less than five total hours of sleep over the course of five and a half days.

The push-ups and sit-ups - sometimes 500 of each per day - are mere warm-up exercises. They swim and train for hours in bone-chilling surf, haul 300-pound logs and boats heavy with sand, and run obstacle courses under relentless prodding from drill instructors. The skin of their legs, feet, shoulders and groin is often worn raw from the constant motion and the chafing of military pants, boots or life jackets.

To steel himself for what awaited him, Murphy called home with a request.

He needed his father to send him a 1970 photograph that showed Daniel Murphy recovering from his Vietnam wounds. "If you could make it through what you went through, I can make it through Hell Week," Michael Murphy told his father.

Midway through Hell Week, the highest-ranking trainee in Murphy's group, Lt. John Anthony Skop Jr., of Buffalo, died of a heart attack during a swimming pool training exercise. He was 29. Three years earlier, Navy airman Gordon Racine died during training in the same pool.

"You have the feeling that it's never going to end," said Navy Lt. Jim Quattromani, 29, a SEAL stationed in San Diego who went through Hell Week with Murphy. "I saw on numerous occasions him sort of pulling other guys along.

"He really exuded a confidence and a maturity," added Quattromani. "He was slightly older than some of the other guys because he had been out of school for a while. And physically, he was such a good athlete that it seemed to come easier for him.

"To me, of all the guys in the class, he was among the top few who it was obvious they were going to get through it," he said.

Becoming a SEAL isn't all brawn and endurance. SEAL candidates must score well on the Armed Services Vocational Aptitude Battery, a series of tests similar to the SATs, which gauge mathematical reasoning and verbal skills.

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SEALs must score as well as the Navy's nuclear propulsion candidates, who serve aboard submarines, a SEAL official explained.

Murphy successfully completed his SEAL training, which included a month of jumps at the army's parachute school at Ft. Benning, Ga. In July 2002, it was official. He was awarded the trident symbol of the Navy SEALs.

As Murphy emerged from SEAL training, war was under way in Afghanistan.

U.S. bombers had struck Taliban and al-Qaida terrorist training camps near Kabul, Kandahar and Jalalabad beginning in the fall of 2001.

Knowing full well he would play a role somewhere, Murphy was assigned to SEAL Delivery Team One, based at Pearl Harbor.