An Israeli military investigation of the episode concluded a month ago that Israeli soldiers most likely fired only after having been fired upon. A video in two separate parts, produced by the army and shown to the commission, stated that the shot fired at the second soldier was “probably” the first shot fired on the ship.

But General Ashkenazi said it was “clear and established” that flotilla participants opened fire first.

The weapon used may have been snatched from the first soldier who landed on the ship.

A gun belonging to one of the soldiers was later found on board, empty of bullets. In addition, the military said it found ammunition, cartridges and bullets that were not from the Israeli Army, suggesting that there might have been at least one other gun on the ship. According to the general, the boat’s captain told the Israelis that it might have been thrown overboard.

General Ashkenazi stated that the army had prepared for the possibility that the activists could open fire, though the military “did not assess correctly the strength of the resistance” the commandos would meet when they came down the rope. According to the video, soldiers trying to approach the Mavi Marmara on rubber lifeboats said they were fired on from both sides of the ship. As clashes broke out on the boat, commandos fired at the feet of their “attackers.”

When the commandos met resistance as they tried to rush the bridge, they responded with fire. And at one point, at least 15 minutes into the struggle for control of the ship, the force commander allowed the soldiers to use accurate and precise live fire against violent activists, to permit more soldiers to climb aboard from the lifeboats.

Eight Turkish activists and an American-Turkish youth were killed, and nine soldiers were wounded, three of them from knife or gunshot wounds.

The Israeli prime minister, Benjamin Netanyahu, and the defense minister, Ehud Barak, also testified before the commission this week. Like the chief of staff, they testified partly in public, and partly behind closed doors. The commission, led by a retired Israeli Supreme Court judge and with the participation of two foreign observers, is mandated to examine the legality of Israel’s naval blockade of Gaza and the way it was enforced in late May. But it has also raised delicate domestic questions of accountability for the raid.