The IDF (Israel Defense Force) investigative report of its attack on USS Liberty -- known as the Ram Ron Report -- states:
"...the Air Force [of Israel] was permitted to attack the [unidentified] ship should it be identified as a warship."
This attack "permission" was governed, in part, by a Rule of Engagement issued by the IDF Navy. The rule, as cited in the Ram Ron Report, reads as follows:
"When there is knowledge of an enemy in the area and the radar picks up a ship or ships traveling at a speed exceeding 20 knots, such ship(s) shall be deemed an enemy [warship] and no further identification shall be carried out."
By itself, this Rule of Engagement was extremely reckless because it totally ignored the possibility of a 20 knot ship being a neutral ship, and left open the interpretation of "knowledge of an enemy in the area."
Fortunately, there was another IDF Rule of Engagement, cited in the Ram Ron Report, that served to moderate the previous rule:
"...the [IDF] forces should at all cost avoid attacks on any neutral merchant ship or warships."
Thus, the "20 knot rule" allowed IDF forces to declare an unidentified, high-speed ship as an enemy warship, but it did not relieve IDF forces of responsibility and duty to follow other Rules of Engagement -- and International Laws of War -- regarding neutral vessels. Specifically, to avoid at all cost attacks on any neutral vessels; i.e., positively identify vessels as belligerent (not neutral) before attacking.
So, the purported attack "permission" given to the pilots implicitly meant, according the IDF's Rules of Engagement and International Laws of War, that the ship must be positively identified as an enemy vessel before attacking. Therefore, a rational interpretation of the attack order should have been: You may attack the ship if it is positively identified as an enemy warship.
Regardless and even though the Ram Ron Report, as well as all other IDF reports on this matter, clearly explain that the pilots were not able to identify the ship's nationality as neutral or enemy (with ideal visibility conditions and no urgent or exigent circumstances), the unidentified ship was willfully and repeatedly attacked. Clearly, the pilots and their controllers were reckless and grossly negligent in performing an attack on an unidentified ship. They violated their own Rules of Engagement, as well as International Laws of War.
To rebuke this type of argument, the Ram Ron Report argues that a Standing Order of IDF naval forces,
"An enemy vessel should be attacked in any waters provided such vessel attacks an Israeli vessel or shells a coast of Israel.",
effectively trumped the rule of avoiding at all cost attacks on any neutral vessel. It was this Standing Order that made it legally permissible for the attack to proceed.
Indeed, the Standing Order presents a legitimate argument. After all, a vessel attacking Israel's vessels or territory is no longer a neutral vessel, by definition. Thus, any concern regarding neutrality is rendered moot, under these conditions.
But there is a catch: at no time prior to the attack did any member of the IDF witness USS Liberty (the unidentified ship) attack any vessel or territory of Israel. There may have been a vague notion that this was the case; but none of the attacking forces, their controllers, or the people who reported shelling of the northern coast of Sinai, near El Arish (not the territory of Israel), had knowledge that USS Liberty (the unidentified ship) was responsible for the purported shelling. Thus, there was no evidence -- absolutely none -- that USS Liberty was the ship that purportedly shelled the coast. And considering that USS Liberty had no large guns mounted on her decks, it was highly unlikely that she was the target the IDF was seeking.
There are claims that the pilots believed the forward or aft dish-antennas appeared like large deck guns capable of shelling the coast. But there is nothing in any IDF evidentiary or investigative document or report that supports this claim -- except a parenthetical note by Colonel Ram Ron (the Ram Ron Report's author) where he questions the pilots' report of seeing a single mast as possibly being a gun. Here is how it was written:
" ...the ship was identified by the aeroplanes as a military ship with a single mast (gun?) and a single funnel."
Common sense dictates that the highly-trained pilots knew the difference between a tall vertical mast and a large deck gun, and there is absolutely no evidence that the pilots stated possibly seeing large guns on the ship's decks.
This is simply an example of Colonel Ram Ron and others grasping at straws. Besides, even if the pilots did see or thought they saw large guns on the ship, they had absolutely no evidence before them that USS Liberty was the ship that purportedly shelled the coast; i.e., the ship they were seeking.
Additionally, the fact that the pilots reported only one mast when two other masts were equally visible was negligence in observing and reporting information vital for ground control's target assessment and attack decision-making process.
In conclusion, the pilots (and torpedo boat captains) had a clearly defined duty under the IDF's Rules of Engagement and the International Laws of War to "at all cost avoid attacks on any neutral merchant ship or warships". The attack scenario presented by the IDF shows clearly that the pilots and their controllers failed to perform their duty. If this scenario is true, it indicates willfully reckless and grossly negligent behavior led to the grievous attack on USS Liberty that resulted in killing 34 and wounding more than 170 crew members.