Heights, which would violate a cease-fire to which Israel's government had agreed. However, Syria did not accept the cease fire until 9 June, after the attack on Liberty. Russian author Joseph Daichman, in his book History of the Mossad, states Israel was justified in attacking the Liberty. Israel knew that American radio signals were intercepted by the Soviet Union and that the Soviets would certainly inform Egypt of the fact that, by moving troops to the Golan Heights, Israel had left the Egyptian border undefended. Lenczowski notes that while the Israeli decision to "attack and destroy" the ship "may appear puzzling", the explanation seems to be found in Libertys nature and its task to monitor communications from both sides in the war zone. He writes that timely knowledge of their decision to invade Syria and preparatory moves toward it "might have frustrated Israeli designs for the conquest of Syria's Golan Heights" and, in the sense of Ennes's accusations, provides "a plausible thesis that Israel deliberately decided to incapacitate the signals-collecting American ship and leave no one alive to tell the story of the attack". The U.S. ambassador to Israel, Barbour, had reported on the day of the Liberty attack that he "would not be surprised" by an Israeli attack on Syria, and the IDF Intelligence chief told a White House aide then in Israel that "there still remained the Syria problem and perhaps it would be necessary to give Syria a blow". The 1981 book Weapons by Russell Warren Howe says that Liberty was accompanied by the Polaris ballistic missile-armed Lafayette-class submarine , which filmed the entire episode through its periscope but was unable to provide assistance. James Bamford, a former ABC News producer, says in his 2001 book Body of Secrets, that Israel deliberately attacked Liberty to prevent the discovery of what he described as war crimes, including the killing of Egyptian prisoners of war by the IDF that he alleges was taking place around the same time in the nearby town of El-Arish. However, according to CAMERA, his claim that 400 Egyptians were executed has been cast into doubt since reporters present in the town claimed that there had been a large battle and this was the main cause of casualties. Bamford also stated that eyewitness Gabi Bron had claimed he saw 150 people executed by Israeli troops at El-Arish. However, Gabi Bron claimed to have only seen