On June 8, 1967, at least 34 US sailors were killed and 171 others were wounded in an Israeli attack on the USS Liberty, a United States Navy technical research ship stationed in the Mediterranean Sea off Egypt’s Sinai Peninsula.

Israel claimed it was a case of mistaken identity, saying its naval forces thought the vessel was Egyptian. However, some of the survivors and researchers have disputed the Israeli version of the incident. They lament that successive governments did little to uncover the truth behind one of the deadliest attacks on the US Navy by its closest ally, Israel.

This year, the attack has come under renewed attention after US Representative Thomas Massie called for an investigation into the “unprovoked” attack during a speech on the floor of the House of Representatives on Monday.

So what do we know about one of the most controversial chapters of the US Navy?

What happened on June 8, 1967?

Israeli air and naval forces bombarded the intelligence-gathering vessel in international waters near the Sinai Peninsula during the 1967 war, when Israel captured Egypt’s Sinai, Gaza and the West Bank.

The assault began when Israeli jets attacked the vessel, striking the ship’s deck with antipersonnel weapons and armour-piercing bullets.

This was followed by a devastating strike from Israeli torpedo boats that blew a massive hole in the ship’s starboard side, instantly killing 25 men in the lower research spaces. In total, 34 sailors were killed in the attack.

The crew had been flying the US flag and had even exchanged waves with low-flying Israeli aircraft earlier that morning, making their identity clear. Israel has long maintained the strike was a tragic error, claiming exhausted pilots mistook the US naval vessel for an Egyptian warship.

Was there an attempt to cover up?

Nearly 60 years on, records related to the attack remain classified, survivors and advocates say.

Richard Brooks, chief engineer on the vessel, told Global News Insight in a 2015 interview that “it wasn’t a tragic accident”.

“It was a deliberate attack. They knew who we were. They tried to sink us. They wanted us out to either bring the Americans into the war by blaming the Arabs, or we picked up some information about their war plans.”

A naval board of inquiry was hastily convened while the severely damaged ship was dry-docked in Malta, but the proceedings concluded swiftly.

Ernie Gallo, president of the USS Liberty Survivors Group, dismissed Israel’s “mistaken identity” excuse as a lie and accused the US government of complicity for accepting the false narrative. He continues to demand a full official inquiry.

The US Congress never formally questioned the attack or formed a committee to investigate the tragedy.

Speaking in the House on Monday, Massie said the unarmed ship was flying a clearly visible US flag when it came under sustained attack.

“According to eyewitness accounts, the Israelis machine-gunned the lifeboats that they put down,” Massie said as 12 survivors watched from the gallery of the US House of Representatives. “They machine-gunned the firefighters who were on the deck.”

Israeli officials have long claimed the attack was a case of mistaken identity, but Massie said senior officials, including former CIA officials, rejected that explanation.

The USS Liberty anniversary has renewed relevance because Massie has criticised Washington’s longstanding reluctance to hold Israel accountable, even when US citizens are killed. He has also opposed the latest war on Iran, which Israel dragged the US into, and which has killed at least 13 US soldiers and wounded more than 380.

Israel’s history of espionage against the US

Israel shares close military and intelligence ties with the US, with Washington providing billions of dollars in military assistance for decades. The two countries have coordinated in military operations.

The USS Liberty attack remains a dark chapter, but it is not the only instance of Israel taking aggressive action or conducting intelligence operations against the US. Recently, the Pentagon’s Defense Intelligence Agency (DIA) elevated the counterintelligence threat posed by Israel to its highest level of “critical”.

The warning follows reports of Israeli intelligence agencies intensifying efforts to collect information on US military personnel and government officials to intercept policy discussions amid efforts by the administration of President Donald Trump to reach a deal with Iran. Israel has been against a deal with Iran, as its aim to topple the Iranian government was not realised by the current war.

Other examples of Israeli espionage against the US include the covert installation of spyware on the mobile phones of US defence personnel operating inside Israel to tap their communications.

Jonathan Pollard, a US Navy civilian intelligence analyst who was arrested in 1985, pleaded guilty to passing classified information to Israel. He was released after serving 30 years in prison.