On June 8, 1967, the fourth day of the Six-Day War, the Israeli high command received reports that Israeli troops in El Arish were being fired upon from the sea, presumably by an Egyptian vessel, as they had a day before. The United States had announced that it had no naval forces within hundreds of miles of the battle front on the floor of the United Nations a few days earlier; however, the USS Liberty, an American intelligence ship assigned to monitor the fighting, arrived in the area, 14 miles off the Sinai coast, as a result of a series of United States communication failures, whereby messages directing the ship not to approach within 100 miles were not received by the Liberty. The Israelis mistakenly thought this was the ship doing the shelling and war planes and torpedo boats attacked, killing 34 members of the Liberty's crew and wounding 171.
Shortly afterward, the Joint Chiefs of Staff organized a fact-finding team to investigate the communications problems that led to the tragedy. The report focused on the ship's position rather than the attack itself. AICE obtained a declassified version of the secret report, which still was redacted. The most important piece of information that was not declassified was the ship's mission, which is now widely believed to have been intelligence gathering.
On June 6, the Liberty was sent a message citing the “unpredictability of United Arab Republic actions” and directed the ship to “maintain a high state of vigilance against attack or threat of attack.” (pp. 16-17)
Originally, the ship was to get no closer than 20 nautical miles to the UAR and 15 to Israel. The Chief of Naval Operations expressed concern about the prudence of sending the Liberty so close to the area of hostilities and the ship was subsequently ordered to remain 100 miles away from both countries. (pp. 19-20)
The message was apparently never received. The fact-finding team reported that “there were no records or communications files surviving which could be examined, nor were there any surviving key communications personnel available who had direct knowledge and reliable power of recall.” (p. 3)
A flash cable sent immediately after the attack reported that Israel had “erroneously” attacked the Liberty, that IDF helicopters were in rescue operations, and that Israel had sent “abject apologies” and requested information on any other U.S. ships near the war zone.
The JCS team found that:
Sources: Report of the JCS Fact Finding Team, "USS Liberty Incident, 8 June 1967," The Joint Chiefs of Staff, Washington, DC, June 18, 1967.