A mission upriver in John F. Kerry's war started with a call to arms. "Saddle up, tigers," he would bark to his gunboat crewmen before they headed off on patrol deep into Vietnam's mangrove-choked canals. It was a command and a warning.

Kerry led his men into combat with a gambler's daring that masked a doubter's disillusionment. The remote southern coast of the Mekong Delta became a proving ground for a Navy lieutenant junior grade eager to test his mettle as a leader -- and a crash course in failed policy for a Yale graduate skeptical of the war's outcome.

For four months, from fall 1968 into spring 1969, Kerry, then 26, experienced Vietnam's chaos from both vantages, piloting a succession of machine-gun-armed Swift boats on raids against Viet Cong river outposts. His aggressive, unorthodox tactics made admirers of his crewmen, raised eyebrows among fellow officers and commanders, and earned him a Silver Star and a Bronze Star for valor.

He approached Vietnam with ambivalence but intent on making his mark in wartime, much as had his political role model, President John F. Kennedy. Kerry's passage steeped him with self-confidence and a lasting "sense of what it means to be under fire," he said recently during an interview in Portland, Ore.

"I think I was a good warrior," Kerry said. "I think I knew how to fight. I also think I was smart enough and sensitive enough to see through it, and know what the downsides and the strategy faults were."

Kerry took calculated risks in battle even as his unease grew over the Vietnam War's stalemated strategy and steep death toll. After a final blur of firefights and close calls, a third combat wound allowed him to shorten his one-year tour. Kerry returned to the United States to publicly oppose the war and run for office.

The loyal band of Navy crewmen and gunboat officers who bonded with Kerry 35 years ago now campaign for him as a trusted fighter. "He got us psyched up to go out on patrol every day even though he needed it as much as we did," said Del Sandusky, one of Kerry's gunboat helmsmen.

Other Swift boat officers -- Republican sympathizers and veterans bitter over Kerry's post-Vietnam peace activism -- pose a darker alternate history. Members of Swift Boat Veterans for Truth, an anti-Kerry political committee that began running an advertisement this week questioning Kerry's service in Vietnam, are led by retired Rear Adm. Roy F. Hoffmann, a blunt-edged Navy career man who oversaw the hit-and-run river raids Kerry viewed as a costly waste of American lives.

In Vietnam, Hoffmann and other former officers contend, Kerry bucked Navy procedure, staying in the country just long enough to prime his political resume. Some question the accuracy of Kerry's recollections and the legitimacy of the first of his three Purple Hearts -- a minor wound, they claim, that was not suffered in action.

"He went to Vietnam to build a career," Hoffmann said. "He was a loose cannon while he was there, and he bugged out early."

Yet Hoffmann and Kerry had few direct dealings in Vietnam. A Los Angeles Times examination of archived Navy documents found that Hoffmann praised Kerry's performance in cabled messages after several river skirmishes. And while the Purple Heart account remains murky, its award was routine. Navy records show Swift boat crews were frequently raked with slight wounds of uncertain origin -- injuries that often earned decorations.

"I don't know what conclusions you can draw about someone's ability to lead from their combat experience, but John's service was commendable," said James J. Galvin, a former Swift boat officer who, like Kerry, was honored for three minor wounds and left the coastal combat zone early. "He played by the same rules we all did."

Aware he was eligible for the draft, Kerry explored his uncertainty in a valedictory speech to his 1966 Yale graduating class. "This Vietnam War," he said, "has found our policymakers forcing Americans into a strange corner." Solemnly insisting he valued military service, he mused about "the very roots of what we are serving."

He sidestepped the draft by applying to the highly competitive Navy Officer Candidate School in Newport, R.I. As U.S. troop levels escalated and fierce fighting flared, college graduates flooded the Navy OCS with applications because duty aboard a ship was seen as far safer than being a junior officer in the Army or Marines.

On training duty off Vietnam's coast in 1968 aboard the missile frigate Gridley, Kerry fixated on the 50-foot aluminum boats on patrol nearby. Shallow Water Inshore Fast Tactical craft were speedy oil rig transports modified with grenade launchers and .50-caliber machine guns.

"We were just enamored of those boats," said former Deputy Assistant Secretary of the Navy Wade Sanders, who trained with Kerry. "It was cool; it was what Kennedy did."

Avoiding brutal warfare was a factor, Kerry has admitted. Swift boat training prepared him for coastal duty, targeting junks and sampans that supplied the Viet Cong. He expected a gentleman's war, with skirmishes and some casualties, not an infantryman's grinding combat.

But by his November arrival at the U.S. base at Cam Ranh Bay, Swift boat duty had grown hazardous. Frustrated at the Viet Cong's ease at moving through the Mekong's web of rivers and canals, the Navy was probing inland. The Navy's new top officer in Vietnam, Vice Adm. Elmo R. Zumwalt Jr., had launched Operation Sealords, a plan that relied on Swift boats to seek out and destroy enemy vessels and hamlets.

Kerry arrived "intent on living up to standards." But "from my first week in country," he said, he was disturbed by the "lack of taking territory. Strategically, it didn't make a lot of sense."

Hoffmann, a decorated Korean War veteran whom Navy officials chose to carry out that strategy, has not forgiven Kerry for questioning Sealords' results.

"He never saw the big picture," Hoffmann, 78, said during an interview at his Virginia home. "The key concept was to take over the rivers and work up to the Cambodian border. Well, we did that."

Plucked off a nuclear destroyer to head the Navy's effort to slash Viet Cong supply routes, Hoffmann demanded initiative and obedience. He gave officers authority to fire at will and demanded body counts to prove their success.

Hoffman commanded more than 100 Swift boats, also called PCFs, for "patrol craft fast," as part of the Sealords mission. The boats advanced inland at a high cost. Several were sunk by rocket blasts, and, by the war's end, 51 men had died out of the nearly 3,000 officers and enlisted personnel in the "brown water navy."

Even before he had his first boat command, Kerry sailed off on a "dangerous mission" that led to his first wound -- and to skeptical murmurs. Patrolling north of Cam Ranh Bay in a skimmer on the night of Dec. 2, Kerry and two crewmen fired on Viet Cong guerrillas massed on a beach. Amid the din, he felt a sting in his forearm.

"I didn't see where it came from," Kerry said. Radarman Jim Wasser, who covered that night from another boat and later sailed with Kerry, recalled hearing a radio message that "someone had a slight wound."

The next day, the base medical officer used tweezers to remove a shrapnel shard from Kerry's arm. According to the former medic, retired Dr. Louis Letson, Kerry said he had been "under hostile fire." But corpsmen heard from other crewmen that there was no return volley, said Letson, now among Hoffmann's anti-Kerry faction.

Later that day, Kerry displayed what his superior, Lt. Cmdr. Grant Hibbard, recalled as a "scratch." Kerry asked him to write an official injury report, but Hibbard said he told Kerry to "forget it."

Hibbard and other critics cited the incident as a glaring mark against Kerry as an officer and a gentleman. By grubbing for an undeserved honor, they said, Kerry used it to reduce his Vietnam tour.

Kerry testily denied initially pressing for the award, saying he simply reported the wound. "Later on, I asked where it was or something," he said, but insisted he played no role in obtaining the medal. "It wasn't my decision."

It was the Navy's. The award came from the Naval Support Facility in Saigon -- issued without any evident formal protest at the time from Hibbard, Letson or other commanders. Neither the slightness of Kerry's wound or its murky origins would have likely disqualified him, said Shelby Jean Kirk, a retired civilian director of the Bureau of Naval Operations awards branch.

The most critical element in an award decision was "action against the enemy." Conflicting battle accounts were not uncommon, and when Navy awards personnel could not make a clear determination, the serviceman often "got the benefit of the doubt," Kirk said.

Within days, Kerry had his first boat command. Through late January, he led the five-man crew of PCF-44, patrolling between Cam Ranh Bay and An Thoi, a small base on the western rind of the remote Ca Mau.

Nights in the canals were ambush hell. Just before Christmas near the Cambodian border, Wasser opened fire after a mortar round exploded. His shots killed an old man tending a water buffalo. "The holiday season's still tough on me," he said.

In another harrowing incident, Gardner blasted a Viet Cong suspect off a sampan as he saw "the guy rise up with an AK-47." When the crew boarded, they found a frightened woman and a child's bullet-riddled body.

"It became a walk on the dark side," Kerry said, quieting at his memories.

After more than a month at the helm of PCF-44, Kerry was given command of a second boat, PCF-94, out of An Thoi. On a series of sweeps in the Ca Mau, Kerry stretched his tactics. Weary of ambushes, he began beaching his boat under fire, a risky move shunned by most officers.

In training, Swift boat officers were warned that a Navy commander never left his boat -- snipers and booby traps were a constant peril. But on Feb. 28, Kerry went on land. After transporting units of South Vietnamese soldiers for a raid on a Viet Cong camp on the Rach Dong Cung canal, PCF-94 and two other Swift boats were attacked from the shore. The boats turned toward the volleys, scattering guerrillas with machine-gun fire.

Resuming downriver, the boats sailed into a rocket barrage. Kerry ordered helmsman Sandusky to wheel toward the beach. As the boat skidded on land, a teen-age insurgent rose up only a few feet away, hoisting a B-40 grenade launcher.

"I could see the hairs of his mustache," said gunner Fred Short. "Why he didn't fire, who knows? I guess we scared (the) hell out of him."

Tom Belodeau, the other gunner, got off a burst. Wounded in the leg, the youth hobbled behind a hut with his weapon. Armed with an M-16 rifle, Kerry ordered Belodeau and mate Mike Medeiros to follow, then sprinted ahead. "We were all firing, but the skipper got him," Short recalled.

No one had a clear view of the shooting. But "next thing we know, there's Kerry with the B-40 in his hand," Sandusky said.

Kerry's charge won him a Silver Star, awarded by Zumwalt in a Saigon ceremony. Kerry's turning point came March 13, when he was ordered with four other Swift boat officers to transport Vietnamese mercenaries and U.S. officers on a series of sweeps along the Bay Hap River. After a long day of shore skirmishes, the gunboats chugged directly into a gantlet of machine-gun fire and exploding mines.

A blast rocked PCF-94, pitching Kerry against the bulkhead and wrenching his arm. Another charge blew Army Lt. James Rassman into the river from another boat. Rassman bobbed under a wild spray of Viet Cong gunfire. His arm bleeding, Kerry ordered Sandusky to swing the boat around.

"Here comes Kerry charging up to the bow," Rassman recalled. "He kneeled down and grabbed my arm and pulled me over. ... It was miraculous neither of us were hit."

Kerry was awarded the Bronze Star and his third Purple Heart. With three decorated wounds, an obscure regulation allowed him to request reassignment -- even back to the United States. Kerry recalled one commander, Chuck Horne, telling him: "You've got a ticket home."

He had had enough. A strip of shrapnel was buried in his thigh. On the dock, he had counted 180 holes and dents in PCF-94's scarred hull.