http://combat-skyspot.tripod.com/index.htm

First, rendering the bridge impassable did not alter the North Vietnamese plans in northern I Corps, nor did it “change the outcome” of the battle as the article claims. The enemy order of battle was oriented from the west, not the north across the DMZ because Hanoi understood that the series of west-to-east flowing rivers in Quang Tri Province would be difficult to cross unopposed. Therefore, the North Vietnamese plan called for only a single regiment to be oriented along Highway 1, with two others to the west and east of the road respectively. The other five regiments, plus the 308th Division headquarters, were far to the west and southwest. Had the North Vietnamese been able to cross the Dong Ha bridge they might have had an easier time of it, but they were in no way thwarted by the loss of the bridge. They understood that the destruction of any of the major bridges would halt them in their tracks. So when the tanks met opposition at Dong Ha they quickly withdrew to the west and crossed there, as the author states. In fact, the tanks were already gone by the time Ripley set the explosives, though some North Vietnamese infantry remained there and were firing at Ripley as he set the charges.
The second issue is how the bridge was actually blown up. Daily journals and other documents indicate that, although the explosives were rigged under the bridge, they probably failed to detonate. At around 1600, elements of the South Vietnamese 1st Armored Brigade, accompanied by U.S. Army adviser Lt. Col. Louis Wagner, pulled up to the south side of bridge and apparently countermanded any orders to blow the bridge. This was six hours after Ripley was preparing to set his explosives (the daily journal at First Regional Assistance Command, the advisory headquarters for I Corps, has the entry “friendly elements are preparing to destroy the bridge” at 0953). Wagner, Ripley, and a handful of others even walked out onto the bridge. Shortly afterward, a Combat Skyspot air strike (an early version of the smart bomb that used laser beams to “guide” the bombs) hit the bridge, cratering its entire length and apparently setting off the explosives set by Ripley on the on the south side. Another armor adviser, Col. Raymond Battreall, recalled “a horrendous damn shrieking, swishing sound came down out of the overcast, and the bridge went sky high.” Colonel Wagner’s report of the incident indicated that “Aircraft began bombing north of the river…. Demolitions on the bridge exploded at this time, dropping a span on the south side. The explosion appeared to be a sympathetic detonation, although it could not be verified whether friendly personnel had blown it deliberately or not.”

The photo on page 51 shows the bridge smoking in a dozen places all along its span (it was made of steel and concrete, not wood, as the caption indicates). How could Ripley’s explosives have done all that? Did he crawl all along the bridge’s underside, a distance of well over a hundred yards? He never made such a claim. In fact, a closer examination reveals that the southernmost span (lower left corner of the photo) dropped cleanly. That was where Ripley set his explosives.

Finally, mostly as an aside, the photo on page 49 of Ripley “narrowly escap[ing] the blast of a mortar round” is hard to believe. The “blast” looks like mud being thrown from the tracks of the M113 behind which he is running. A mortar round that close would certainly have killed or badly wounded Ripley—not to mention the photographer taking the picture from atop the vehicle.