the beginning of august found the american destroyer ussMaddox engaged in a “De Soto patrol” in the Gulf of Tonkin, off the North Vietnamese coast. The highly classified De Soto patrols had been conducted sporadically since 1962 for the purposes of gathering information on North Vietnamese radar and decrypting North Vietnamese communications. When, on the morning of July 31, the Maddox had crossed the 17th Parallel on its way northward, it had come within four miles of six South Vietnamese commando boats that were speeding southward after bombarding North Vietnamese island installations as part of OPLAN 34-A. Later, it was widely believed that the North Vietnamese attacked the Maddox because they mistakenly concluded that it had just participated in these raids. Communist histories, however, make clear that no such confusion existed. North Vietnamese radar had begun tracking the Maddox long before it entered the area of the 34-A attack, and tracked it for another two days before the attack order was issued in Hanoi.

The North Vietnamese were, nevertheless, more troubled by hostile naval operations than the U. S. government thought. As they monitored the northward movement of the Maddox, the North Vietnamese feared that the American destroyer would attack the coast or the islands as previous vessels had done. It had not occurred to the Americans that the North Vietnamese would take this view of the Maddox, which was larger and was moving much slower than the commando boats, but that is what happened.