When Israeli commandos rappelled onto a flotilla of aid ships that were trying to break its Gaza embargo, they descended into a battle zone that left nine people dead and 30 injured, including several Israeli soldiers.
The violent confrontation also triggered a diplomatic firestorm and angry protests erupted in a dozen countries.
Israeli Prime Minister Benjamin Netanyahu, who was in Canada on his way to a White House meeting on Tuesday, canceled the meeting with President Obama. The two leaders later spoke briefly by phone and Obama said he "deeply regrets" the loss of life.
Netanyahu defended the use of force saying, "Our soldiers had to defend themselves, defend their lives, or they would have been killed."
The flotilla of six ships loaded with 600 protesters and tons of humanitarian supplies was organized by the Free Gaza Movement, an international coalition of pro-Palestinian activists, and a Turkish charity. Many of the passengers aboard the ships were Turkish.
There are conflicting reports about what happened during Israeli raid.
The Israeli navy confronted the convoy of ships in darkness, warning them to turn back. The ships refused. Communication between the ships and their families at home was cut off. Speedboats raced alongside and naval commandos dropped from helicopters.
An Al Jazeera correspondent, Jamad Al Shaid, on board the Mavi Mamara ship, reported that the Israelis fired at the vessel before boarding it.
"Tens of people have been injured, two killed, on board this ship which carries 600 activists, parliamentarians, women and children, and the elderly. All of them whom are civilians," the reporter said.
The Israelis, however, claimed their forces came under fire as they boarded the ships. Several Israeli soldiers were helicoptered away from the scene for medical care after suffering gunshots, stab wounds or bruises.
Avital Leibovitch, spokeswoman for the Israel Defense Force, said the Israeli naval commander offered several times to escort the ships to an Israeli port, but the flotilla captains refused.
She said the Israelis were met with a "preplanned violent attack," using knives, sticks and two pistols that were wrested from the Israelis. The Israelis boarded with their guns unloaded, Leibovitch said. People who attacked the Israeli commandos and took the pistols, also found the ammunition, loaded the pistols and used them against the Israelis, she claimed.
The Israelis allowed two of their commandos to speak, but identified them only by an initial.
First Sgt. Y said that his team was told they would be dealing with human rights activists, and he wasn't prepared for what met him when he rappelled to the deck of the Mavi Mamara armed with only a paintball gun used to subdue crowds.
"I came down and just saw war. I saw they were trying to kill us," he said.
As he rappelled down, First Sgt. Y found that people on the boat he fouled the lines to prevent the commandos from reaching the deck of the ship.
"We felt that they were really organized... With each guy who came down it was like a prepared attack," he said.
The first sergeant said when he landed on the ship he saw a comrade being attacked with pepper spray and steel clubs. "When they finished with him, they came for me," he said.
Others were thrown off the deck and landed in the water, the sergeant said. He saw another shot and spitting blood.