BAY HAP RIVER, Vietnam – Nestled amidst mangrove swamps and flanked by small villages and the occasional thatched-roof shack, this muddy waterway in the southwest part of the Mekong Delta seems a most unlikely venue for events key to an American presidential election.

Yet, it was here 35 years ago that John Kerry saw the combat that has become a central theme of his campaign for the presidency.

Lieutenant Kerry spent four months as the captain of a Navy patrol boat in Vietnam. He and his Swift boat crew were transferred repeatedly among the various American outposts in South Vietnam.

Mr. Kerry patrolled the waters in this part of the extreme south, known as the Ca Mau Peninsula, for just a few days in December 1968 and about eight weeks between January and March of the following year. It was during the latter stretch here that the 25-year-old lieutenant encountered the fiercest fighting of his Vietnam tour and won all but one of his combat decorations.

Viet Cong guerrillas laced the rivers and canals here with explosive booby traps and mines.The Communist forces used a variety of tactics, including strong fish nets stretched across the water to slow down or stop the American boats so they could be ambushed from the shore with machine guns, grenades, and rockets.

Few signs of that troubled time remain. The sampans are still here, but most have been fitted with small gasoline engines that ease the ride.Exhaustspewing speedboats that connect the major towns in the area regularly buffet the canoelike craft. There are roads linking most places,but water transport remains more efficient and reliable.

Some here are aware that an American veteran of the Vietnam War is seeking the presidency, but few appear to realize that Mr. Kerry fought in their backyard.

One man who claims to recall Mr. Kerry is a former Viet Cong officer, ThoyViet Hung.

“I remember him,”said Mr.Thoy,who lives just outside the town of Nam Can. The 56-year-old veteran said that American forces stayed on ships moored in the town from 1969 until 1972 and that he saw Mr. Kerry among them.

A formal portrait of Mr. Thoy in his military uniform hangs on the wall in his modest home. He would not discuss his wartime exploits in detail with an American visitor, but said that he harbors no ill will toward America or Mr. Kerry.

“Because of the war, Vietnamese people were very miserable,” Mr. Thoy said. “In recent years, America has helped Vietnam in many fields.The war has been over for 30 years. Now, America and Vietnam are friends.”

Mr.Thoy, who works with Vietnamese fighters who were disabled by the conflict,said he recently saw news coverage of Mr. Kerry’s presidential bid.

“I saw him on TV. I want him to take care of handicapped Vietnamese people from the war,” Mr.Thoy said.

Officials at two government offices in the area said they had “no information” on fighting that took place in the area during the war, though other locals described it as intense. One indication of that intensity is a riverside memorial in the town of Dong Cung (pronounced “dong koong.”)

Under an inscription reading, “Care for,Thank and Remember the Fallen Heroes,” hundreds of names of Viet Cong soldiers killed in the region are listed.

Many in the area were nervous about discussing their recollections with a visiting American. In the years that followed the 1973 withdrawal of American troops and the victory of the Communist forces in 1975, hundreds of thousands of Vietnamese suspected of having cooperated with the Americans were sent to so-called re-education camps.Bitterness about the harsh policy lingers.

Mr. Kerry’s experiences here are detailed in after-action reports found in Navy archives. Most of his missions were part of Operation Sea Lords, a strategy crafted by Admiral Elmo Zumwalt Jr., to venture far up rivers in southern Vietnam to disrupt Viet Cong supply lines and force guerillas west towards Cambodia.

These missions brought Mr. Kerry a bronze star, a silver star, and two of his three purple hearts.They also include a number of episodes that have proven to be trouble for Mr. Kerry, personally and politically.

On February 28, 1969, while traveling up the Bay Hap, Mr. Kerry’s boat and two others came under heavy fire from the shore. In a breach of protocol, he ordered the craft to turn into the fire and beach. The tactic prompted about 20 Viet Cong troops to flee. Marines from the boats chased down the troops.

A short time later, enemy forces fired a rocket at Mr.Kerry’s boat,blowing out one of its windows. Again, he turned the boat toward the fire and moved the craft to the shore. A man with a rocket launcher jumped up from the reeds and began to run. A gunner on Mr. Kerry’s boat wounded the man in the leg but he kept moving. In another breach of procedure, the young lieutenant jumped out of the boat and chased down the rocket-wielding man. Behind a hootch, or small hut, Mr. Kerry shot and killed the assailant.

The engagement brought Mr.Kerry a Silver Star. During his 1996 race for reelection to the Senate, a Boston Globe columnist suggested Mr. Kerry might have committed a war crime by administering a “coup de grace” to the Vietnamese soldier. The suggestion outraged Mr. Kerry. His campaign arranged for a number of Vietnam veterans to travel to Boston to defend him. Among them were many of his crewmates, as well as Zumwalt.

Zumwalt said he felt obliged to defend Mr. Kerry, although the two men had long disagreed on some key issues, including the wisdom of the Sea Lords plan. Mr. Kerry thought it foolish because no ground was taken and the Viet Cong could regroup as soon as the small boats left. Zumwalt believed the operation was a major success.

While Mr. Kerry protested the war upon his return home, Zumwalt blamed the erosion of political will in America for the military defeat in Vietnam.

“If one knew then what we know now – namely, that the United States would make a decision here to lose that war – I would far have preferred that we never had gotten involved in the war,”the admiral said in a 1984 PBS interview. He died in 2000.

Mr. Kerry’s last major combat engagement occurred in the Dong Cung Canal and the Bay Hap River on March 13, 1969. His boat was caught in a two hour firefight with Viet Cong guerrillas. Later, two mines detonated, tossing another small Navy boat two or three feet into the air. Mr. Kerry was slightly wounded in the explosions.

As the boats rushed to leave the area, someone noticed that a green beret had fallen overboard into the river. Mr. Kerry turned his boat around and went back for Special Forces soldier James Rassmann. Braving fire from the shore, Mr. Kerry pulled Mr. Rassmann to safety. The action won Mr. Kerry a bronze star and another purple heart, his third, which allowed him to request reassignment out of the combat zone.

In January of this year, Mr. Rassmann returned the favor. With Mr. Kerry struggling to win Iowa’s early presidential caucus, Mr. Rassmann flew to Des Moines and recounted the tale of heroism in the Bay Hap. The two men had not seen each other since 1969.

“John didn’t have to, but he came to the front under fire. He pulled me over. Had he not, there’s no question in my mind that I would have fallen back into the river,” Mr. Rassmann said. “I figure I owe him my life.”

The tale of wartime bravery is widely credited with leading Mr. Kerry to his first-place finish in Iowa. Mr. Rassmann has also defended Mr.Kerry from some charges of cowardice and duplicity put forward by his critics.

“I can tell you from my own experience with the senator and his crew…there’s nothing phony about what they did,” Mr. Rassmann told The New York Sun in an interview earlier this year.”John Kerry is absolutely genuine.”

Back in the waters Mr. Kerry plied three and a half decades ago, some locals still pursue traditional fishing. Others gather and sell giant sea snails said to be unique to the area. However, many are turning to aquaculture to make a living. Large factories package fish fillets and shrimp for sale to America, Japan, and elsewhere. Even in small villages, storefronts are jam packed with tanks where shrimp are being raised.

With all this enterprise under way, there are signs that the venerated late leader of the Vietnamese Communists, Ho Chi Minh, may no longer inspire the cultlike fervor he once did.

In the town of Cai Nuoc, where American Swift boat captains sometimes dropped off captured prisoners for interrogation by South Vietnamese troops, a hall built in tribute to the man many Vietnamese call Uncle Ho sat padlocked last week. The grounds suggest that the place has fallen into disuse.

One business glad to hear about Mr. Kerry’s exploits in the area is the local tour company. The region, which is heavily infested by mosquitoes, sees few foreign tourists. Asked about the prospect of escorting Americans on combat-themed tours, a tour guide was positively jubilant.

“I volunteer,” said the guide, Phan Thanh Thao. She suggested that some Western capital might be needed to make sure the boats and other facilities are up to snuff.”Maybe you’d like to invest in Ca Mau tourism?” she asked an American visitor. If Mr. Kerry wins, it might not be a bad idea.