WHEN John Kerry "reported for duty" at the Democratic National Convention and presented himself as qualified to lead by virtue of his service in Vietnam, he opened up for public scrutiny his actions in Vietnam and, later, as an antiwar activist. Kerry's critics, including the Swift Boat Veterans for Truth, promptly responded with a critique of Kerry's record. The charges and counter-charges have left many confused, especially as some issues seem to turn on obscure, if not arcane, facts.

What follows is a primer on the main issues, the evidence and open questions.

Christmas in Cambodia

On March 27, 1986, Kerry took the floor of the U.S. Senate to deliver a dramatic indictment of Reagan administration foreign policy. As is his habit, he drew on his Vietnam experience: "I remember Christmas of 1968 sitting on a gunboat in Cambodia. I remember what it was like to be shot at by Vietnamese and Khmer Rouge and Cambodians, and having the president of the United States telling the American people that I was not there."

He continued: "I have that memory which is seared — seared — in me, that says to me, before we send another generation into harm's way we have a responsibility in the U.S. Senate to go the last step, to make the best effort possible to avoid that kind of conflict."

Kerry has told of this Cambodia trip many times, from a 1979 Boston Herald review of "Apocalypse Now" to a June 1, 2003, Washington Post profile. The Post's Laura Blumenfeld reported that Kerry pulled a mildewed hat out of his briefcase and described it as "my good luck hat, given to me by a CIA man as we went in for a special mission in Cambodia."

Yet parts of Kerry's story are incredible on their face — such as saying Richard Nixon was responsible for the illegal mission, when Lyndon Johnson was president in 1968.

And there is no record that Swift boats were ever used for secret missions in Cambodia. (Their size and noisy engines make them ill-suited for the job.) Kerry's authorized biography, "Tour of Duty" by Douglas Brinkley, makes no mention of any such mission during Kerry's service.

Not a single crewman who served with Kerry has supported his claim to have entered Cambodia, and three have expressly denied it. Kerry's commanding officers have denied he was ever sent there. And Kerry's own Vietnam journal (excerpted in the Boston Globe) shows that on Christmas 1968 he was docked at Sa Dec, 50 miles from Cambodia.

In mid-August, these facts promped the Kerry campaign to "correct" the story, saying the mission took place in January 1969 when Kerry "inadvertently or responsibly" crossed the border.

Yet "inadvertently" straying into Cambodia — were that even possible — belies the basic point of Kerry's original story: that he lost his faith in government because the president lied about having sent U.S. troops into Cambodia. It also contradicts his story about ferrying a CIA man.

And the "correction" plainly hasn't sunk in: The Democratic Party chairman, Terry McAuliffe, told us in an interview earlier this month that Kerry had made two missions to Cambodia to drop off CIA men.

Some questions that Kerry himself has yet to answer: When exactly did he enter Cambodia? Accidentally, or intentionally? If by accident, how did that lead him to lose faith in the government? If on a secret mission, what was its purpose? What is the name of the CIA man? Why is there no record of any Cambodia mission, even in Kerry's journals? And why do Kerry's crewmates and fellow officers unanimously deny that any such mission ever occurred?

First Combat . . . Maybe

Kerry won his first Purple Heart for a combat engagement on Dec. 2, 1968, while training on a skimmer, or Boston whaler. On his campaign Web site, Kerry claims that on that day, he "experiences his first intense combat; receives combat-related injury" — for which he would eventually receive a Purple Heart.

But in "Tour of Duty," Brinkley writes:

"They pulled away from the pier at Cat Lo with spirits high, feeling satisfied with the way things were going for them. They had no lust for battle, but they also were not afraid. Kerry wrote in his notebook, 'A cocky feeling of invincibility accompanied us up the Long Tau shipping channel because we hadn't been shot at yet, and Americans at war who haven't been shot at are allowed to be cocky.' "

According to Kerry's journal, the date on which he "hadn't been shot at yet" was Dec. 9. Which means he hadn't been in combat on Dec. 2.

This fits in with the Swift vets' contention that Kerry's initial request for a Purple Heart had been denied by the chain of command. In fact, he didn't get a Purple Heart commendation for his Dec. 2 injury until months later, after transferring to a different command — which took Kerry at his word on being under enemy fire in the earlier engagement.

Kerry's campaign has now admitted that his first Purple Heart wound may have been unintentionally self-inflicted, sustained when he exploded a hand grenade too close to shore. The Kerry camp has not responded substantively to questions on the discrepancies between his citation and his journal entries as published by his biographer.

False Memories Of Fighting Together

David Alston has accompanied Kerry on campaign appearances, giving powerful testimony about Kerry's leadership under fire (including perhaps the most effective speech on Kerry's behalf at the Democratic Convention).

Alston and Kerry have both spoken of two engagements in which they took fire together on PCF-94, one on Jan. 29, 1969, the other on Feb. 28, 1969, when Kerry won his Silver Star.

Problems with these stories arose this April, when Lt. Tedd Peck complained that Kerry had appropriated one of Peck's actions as his own. It turned out that Peck, not Kerry, commanded PCF-94 on Jan. 29.

Both Peck and Alston were seriously wounded in that battle. We know that no other officer was aboard PCF-94, because enlisted man Del Sandusky took command after Peck was disabled. So Kerry's claim to have commanded the boat in that engagement is clearly false.

Kerry spokesman Michael Meehan created a timeline that credited all of PCF-94's January engagements to Kerry. Only after Peck complained publicly did Kerry stop trying to take credit for engagements that occurred before he was assigned to PCF-94. The campaign Website now notes only that he took command of PCF-94 in "late January."

According to records formerly available on the site, Alston was Medevaced to an Army hospital in Binh Thuy after being injured in the Jan. 29 fight, and did not return quickly. Kerry took command of PCF-94, the next day, replacing the injured Lt. Peck. The boat also got at least one and probably two new gunners to replace Alston. Fred Short arrived as the new gunner on Feb. 13.

On Feb. 28, PCF-94 took part in the engagement that won Kerry a Silver Star, and a commendation for every member of his crew. Alston has repeatedly asserted, since at least May 2002, that he participated in that action. In an interview with ABC News on June 24, Alston said: "I know when John Kerry told Del to beach that damn boat, this was a brand-new ball game. We wasn't running. We took it to Charlie."

"We?" All of Kerry's crew received commendations for this action. Absent from the list is the name David Alston. But Short's name is listed, and he was photographed at the award ceremony along with Kerry and his five enlisted men (a full PCF crew). Not in the photo: David Alston.

In an interview with Byron York of National Review, Short said that Alston didn't return to PCF-94 until after March 4, 1969, well after the Feb. 28 engagement. The exact date of Alston's return remains a mystery because (like Kerry) Alston has refused to release his military records. What is clear is that both Alston and Kerry have lied since at least May 2002 about Alston's service under Kerry.

Why did Kerry claim to have been in command of PCF-94 on Jan. 29, 1969? Why did Kerry try to replace Fred Short with David Alston as gunner in the Feb. 28 engagement? Only Kerry and Alston can explain. But since the controversy arose, Alston has disappeared from the campaign trail.

One Medal, Three Citations

In that Feb. 28 engagement, Kerry beached his PCF to frontally assault a Viet Cong ambush. He then leapt off the boat and chased an armed VC from the beach, killing him and capturing his rocket launcher. On that much, everyone agrees. The mystery surrounds the three differing citations Kerry has for the Silver Star he earned that day.

Adm. Elmo Zumwalt personally awarded the medal to Kerry. The citation (No. 1) notes that "an enemy soldier sprang up from his position not ten feet from Patrol Craft Fast 94 and fled. Without hesitation, Lieutenant (junior grade) KERRY leaped ashore, pursued the man behind a hootch and killed him . . . " The citations says the operation resulted in 10 Viet Cong killed.

For most people, one citation per award is sufficient. However, Kerry has another (No. 2) for this incident, this one signed by Adm. John Hyland, commander in chief of the Pacific Fleet.

This citation fails to mention the VC that Kerry killed, but has added praise: Kerry now acted "with utter disregard for his own safety and the enemy rockets" and has now faced a "numerically superior force."

Citation No. 3 was signed by John Lehman as secretary of the Navy under Ronald Reagan, more than 10 years after the action. It's nearly identical to No. 2, except it adds, "By his brave actions, bold initiative, and unwavering devotion to duty, Lieutenant (jg) Kerry reflected great credit upon himself."

What really happened on the Dong Cung River that day? Kerry's own crew (most of whom support his candidacy) insisted that Kerry chased the injured VC behind the hootch, out of sight of the crew, before killing him. Kerry denies leaving his crew's sight — which would be a brave but foolish tactical mistake for the commander of a beached boat under fire. And both later citations fail to mention Kerry personally killing the VC.

Last week, The Post's Deborah Orin confirmed from Navy sources that the original teletype of the after-action report had been found in the Naval Archives. It confirms the statements of Kerry's crew: "OinC [Officer in Command] of PCF 94 chased VC inland behind hootch and shot him while he fled capturing one B-40 rocket launcher with round in chamber."

The report also makes clear that the three PCFs carried a contingent of 90 Vietnamese RFPF troops, which would have hardly made their patrol numerically inferior to the snipers that ambushed them. And the final calculation of KIA from that mission, according to the immediately-filed after-action report, was 4 KIA, not 10 or a score as the citations state.

Kerry performed well under fire. But his changing stories regarding the action have mysteriously found their way into the extraordinary series of citations that stretch out over a decade for this single action and award.

Lehman, moreover, insists that he never signed the third citation nor wrote the additional language. On Friday, the Navy inspector general concluded, following an investigation prompted by a Judicial Watch request, that the proper procedure had been followed in the processes initially used to approve Kerry's medals and the officers involved had proper authority to approve the awards. But Adm. R. A. Route's probe didn't address any qualitative review of Kerry's awards, and Lehman's disavowal of citation No. 3 has prompted a separate investigation.

Conclusion

Much more could be said about John Kerry and the Vietnam years, but this primer may suggest why Kerry has been keeping his distance from the press these last six weeks. Kerry can put some of these questions to rest — by signing the standard military form to allow his records to be made public. Until those records are released, many questions will remain unanswered.

Minneapolis attorneys John Hinderaker and Scott Johnson are proprietors of the Web log powerlineblog.com. Minneapolis-based freelance writer Edward Morrissey is proprietor of the Web log captainsquartersblog.com.

This article was published by The New York Post