JOHN KERRY, fresh from a three-day vacation at his retreat in Ketchum, Idaho, addressed the annual convention of the International Association of Fire Fighters in Boston last week, and it was quite a speech--combative, fiery, personal. The firefighters' union was one of the first to endorse Kerry during the Democratic primaries last year, as the candidate barnstormed among the snowy drifts of New Hampshire and Iowa, and on Thursday Kerry spoke to them plainly but forcefully, as one would to old friends. "Over the last week or so," Kerry began, "a group called Swift Boat Veterans for Truth has been attacking me. Of course, this group isn't interested in the truth--and they're not telling the truth. They didn't exist until I won the nomination for president."

The firefighters listened quietly.

"Of course," Kerry went on, "the president keeps telling people he would never question my service to our country. Instead, he watches as a Republican-funded attack group does just that. Well, if he wants to have a debate about our service in Vietnam, here is my answer." He paused. "Bring it on."

The firefighters roared. Once a rhetorical staple of Kerry's on the campaign trail, the phrase "Bring it on" had been remaindered of late, the Kerry campaign having come to the decision, according to Democratic strategists, that the utterance sounded silly. But Kerry was all seriousness when he addressed the firefighters. This was personal.

Which shouldn't be surprising. It's not every day a war thought finished over 30 years ago starts up again. And that is a fair description of what has taken place on the campaign trail over the last two weeks, as the Kerry campaign wrestled with charges from a group of anti-Kerry Vietnam veterans that he distorted--even lied about--his war record. The group with the portentous name has accused Kerry of winning medals under false pretenses, of killing defenseless Vietnamese, of lying about his location and activities during the four months he spent in Vietnam. The veterans make their case in a television ad, which they ran in three key swing states (West Virginia, Ohio, Wisconsin) and also in a book, Unfit for Command, which was written by the group's leader, a veteran named John O'Neill, along with a political scientist named Jerome Corsi.

These are not trivial claims. The Swifties don't give Kerry the benefit of the doubt on any issue. They challenge the circumstances behind every medal he earned in Vietnam. Their accusations are of three broad types.

First, there are issues of fact that are difficult, if not impossible, to resolve. The controversy over how Kerry earned his Bronze Star and third Purple Heart, for example, in which the young lieutenant pulled special forces soldier Jim Rassmann from the Bay Hap river, revolves around whether or not there was enemy fire at the time. Kerry says there was; the anti-Kerry veterans--some of whom were present that day, in boats alongside Kerry's--say there wasn't. The documentary evidence available so far backs Kerry's story. For example, Washington Post reporter Michael Dobbs reported last week that a newly uncovered medal citation for Larry Thurlow, one of the veterans who challenge Kerry's account of the Rassmann incident, supports Kerry. Thurlow claims to have lost the citation over 20 years ago, but has refused to release his service records. Something similar happened in the case of Kerry's Silver Star, as one anti-Kerry vet told conflicting stories to the Boston Globe over the course of a year. In the final analysis, however, such claims boil down to Kerry's word versus his opponents'.