Kerry in Cambodia

I got into a discussion over on Slate's today with someone which tangentially mentioned the various charges of the Swift boat veterans. At one point, this conservative poster gleefully announced that Kerry had been proven a liar on his claims that he'd been in Cambodia during his Vietnam war service.

The discussion of this episode strike me as very curious. Kerry's charge, made at various points and stated in various manners, is that he knew Nixon's claim there were no U.S. forces in Cambodia prior to 1970 was false, because he himself had been in Cambodia during December of '68 or early 1969.

Interestingly, this allegation has been decried as patently false. Take the following article from The Seattle Times:

The book "Unfit for Command," put out by members of Swift Boat Veterans for Truth, contends "all the living commanders in Kerry's chain of command ... indicate that Kerry would have been seriously disciplined or court-martialed had he gone" to Cambodia.

Yet the Kerry campaign said it was far from rare for American forces to pursue Viet Cong over the border.
...
Hoffmann, the retired admiral, said he was leery of Kerry's claim to have ventured into Cambodia in early 1969 to deliver CIA operatives or special-forces soldiers.

"I was always properly informed. The whole time I was there, I don't recall" such a mission, Hoffmann said.

What's strange about this line of refutation is that it seems false on its face.

There was apparently a routine program of cross-border incursions in 1967, 1968, and 1969 involving U.S. Special-Ops forces known as "Operation Daniel Boone." It doesn't have a huge internet footprint, so far as I can see. This bibliographic reference seems to indicate it's in the public record, and this medal citation offers a description of an extraction under fire of a team of Special Forces agents under the aegis of Daniel Boone.

I'm gonna' dig a little deeper into this. It's always been my understanding that Cambodia's ostensible neutrality was kind of a fiction, and that there were in fact numerous U.S. operations inside Cambodia.

Admittedly, though, the substantiating evidence of that has proven far more difficult to find that I had anticipated.

UPDATE:
Dubious hosting source, but putative transcripts of the War Crimes Hearings before the senate. In the testimony of one "GREG HAYWARD Capt, U.S. Army West Point, Class oS 1964":

Another instance, specific instance of a violation of the rules of land warfare was when we planned the artillery bombardment of a hospital installation in Cambodia. We had a FSB called Diamond, 2,000 or 3,000 meters inside South Vietnam from Cambodia, and it was there as bait, you will, because that was when we got our best BODY COUNT ratios, when we were attacked a night on our FSBs and we were successful in luring the enemy across the border into attacking us, and we had preplanned artillery are on the 9th VC's div hospital complex in Cambodia. The plan was, should we not need all our air power and artillery power to protect the Diamond are support base, that a portion of that would be allocated to are into Cambodia on this hospital complex--another clear violation of the rules of land warfare.