Battle at the cages
Widmore threatens to kill Kate. ("The Candidate")
Claire, Frank, Jin, Hurley, Kate, Sawyer and Sun were taken captive by Widmore's team and brought to the cages. Sawyer refused to get inside, remembering his past experience in the cages. Seamus reminded Sawyer that he had the gun, but Sawyer snatched it and pointed it at him. However Widmore held a gun to Kate, threatening to kill her. Sawyer accused him of bluffing, but Widmore said he had received a list of names, including Ford, Reyes, and the Kwons. Since Kate's name wasn't on it, it didn't matter to him if she died. Sawyer returned the gun and the group were put in the cages.
Sayid, Jack, and the Man in Black arrived on Hydra Island. Sayid managed to switch off the power for the sonar fence, allowing the Man in Black to get past them. In his monster form, the Man in Black attacked Widmore's men outside the cages. Jack arrived and unlocked the cages, freeing his friends.
Confrontation at the Ajira plane
The Man in Black went to the crash site of the Ajira plane, where he was attacked by two of Widmore's men. They both tried unsuccessfully to shoot him, after which they were both killed. ("The Candidate")
Conflict at the submarine
Sayid makes his last sacrifice. ("The Candidate")
The Man in Black led the group to the submarine. The first team, consisting of Sawyer, Frank, Hurley, Jin and Sun, successfully hijacked the sub. The second team, consisting of Jack, the Man in Black, Claire, Kate, and Sayid approached next. When Jack was not looking, the Man in Black switched their backpacks, giving Jack the C4 bomb he found on flight 316. When the Man in Black asked Jack why he wanted to stay on the Island, Jack told him John Locke said to do so, and then knocked him in the water. Widmore's men attacked them and Kate was shot. Jack helped Kate onto the sub with Sayid, but Claire stayed behind to help fire on the men. The Man in Black emerged from the water and killed the rest of Widmore's men, and when Sawyer saw him coming, he shut the sub hatch and departed without the distraught Claire. The Man in Black smiled, however, and told Claire she did not want to be on the sub.
Jin and Sun's last moments together. ("The Candidate")
As the sub descended, Jack found the bomb in his backpack. Though he tried to convince Sawyer that they could not die by the Man in Black's machinations and could only kill each other, Sawyer proceeded to disconnect the wires from the bomb, causing it to count down even faster. Sayid instructed Jack on where to find Desmond, telling him that "it's going to be you," and then fled with the bomb to the far end of the sub, sacrificing himself. Some wreckage pinned Sun to the wall and Sawyer was knocked out. Frank went to investigate the blast and was overwhelmed by a huge flood of water that burst in. Hurley took Kate and swam to safety with her, and Jack reluctantly took Sawyer as Jin and Sun stayed behind. Jin's attempts to save Sun were futile, and they proceeded to peacefully drown together.
At the beach
Jack, Kate, Sawyer and Hurley were distraught at the loss of their friends and the fact that the Man in Black had used them. While being healed, Kate took the initative to kill the Man in Black as a way of revenge, starting a journey to rescue Desmond and find out a way to kill The Man in Black.
At the submarine pier
The Man in Black later realized not everyone had died on the sub and proceeded to go "finish what he started", leaving Claire alone.
- It was the most devastating war and most of the casualties in battle.