It was the "ultimate guys weekend" -- at least that's the way Marine Lt. Col. Bob Marshall describes it.

Jumping into chilly waters at dawn. Lugging 50-pound packs. Navigating obstacle courses. Sleeping in tight quarters.

Gov. Mark Sanford, then a congressman, was right in the thick of things, as Marshall, a Marine pilot, remembers the weekend of amphibious exercises at Camp Lejeune, N.C.

Marshall doesn't know, and won't speculate on, whether that rigorous weekend spent among Marines three years ago may have influenced Gov. Mark Sanford's decision to enlist in the Air Force Reserve.

"I would like to think the impressions were favorable and had some influence on him doing that," says Marshall, who escorted Sanford, now-U.S. Sen. Lindsey Graham and U.S. Rep. Chip Pickering of Mississippi on the exercises.

Sanford has said he will fulfill his duties if his unit, the 315th Aeromedical Evacuation Squadron, is called up. That decision has stirred debate at the Capitol over where his ultimate responsibility lies -- with his military unit or the state he governs.

Sanford will leave next weekend for two weeks of Reserve training in Alabama.

There is no question that his exposure to the armed forces during his congressional years played into his growing respect for the military and his own interest in joining the Reserves, spokesman Chris Drummond said.

"He has talked about those trips to the military and how impressed he was," Drummond said.

While in Congress, he began the process of joining the Reserves and has since said he hopes his sons take on some type of military service.At Camp Lejeune, Sanford was exposed, at least in part, to the exhaustive training and hazards encountered by Marines in the unit.

"It was intended to give them an up-close and personal experience" with the unit, said Marshall, who was then executive officer of the 22nd Marine Expeditionary Unit.

As part of the exercise, the congressmen were quartered aboard a 1970s dock landing ship, the USS Portland -- an experience that involved folding themselves into 14-inch bunk spaces along with about 100 junior and enlisted Marines.

The next day they joined Marines aboard a smaller RHIB -- rigid hull inflatable boat -- used for shore landings.

To board the boat, the men had to climb down a rope-and-wood ladder -- not the easiest task with swells rocking both the main ship and the RHIB, Marshall said.

"It was very early in the morning, foggy, and you couldn't see what you were stepping into," said Marshall, now stationed at Marine Corps Air Station New River, next door to Camp Lejeune.

But all three were game to try the ladder, including Graham, who cannot swim, Marshall said. Sanford and Pickering were then tossed overboard with Marines to swim the last 50 yards to shore.

Once ashore, the three shouldered 50-pound packs, marched a half-mile and ran through the paces of an obstacle course.

"Not only did they have an appreciation of the society of the Marines, but they also had an appreciation of the rigors of the Marine training," Marshall said.

Marshall, who shares Sanford's conservative political philosophy, says he was struck by Sanford's forthrightness in discussing how he struggled to balance family and work.

One night, aboard ship, the two men talked for several hours about blending family and work, and how to answer God's call in their lives, Marshall said.

"At the time, he was wondering if he should stay in public office."

The two also talked about military sacrifice.

"Mark said he had no regrets in life except that he had never been in the military," Marshall said.

Marshall and Sanford met again in January when Marshall brought his family -- wife Jana, 7-year-old son Samuel, and 22-month-old daughter, Carolyn -- to Sanford's inauguration.

Marshall was rewarded for waiting in line for several hours to meet the new first family.

"He gave me a big bear hug."