Battle of Seoul

The Battle of Seoul was a major battle between the Avengers and Ultron with his sentries in Seoul, South Korea.

Background
Having experienced nightmares from Scarlet Witch, the Avengers recuperated at Clint Barton's Homestead. Eventually, they realized that Ultron was attempting to create a new body in an attempt to "evolve". Ultron brainwashed U-Gin Geneticist Helen Cho, using the Scepter, and had her build a new body using cells and the Vibranium Ultron stole from Ulysses Klaue. Realizing this, the Avengers split up in an attempt to stop him, with Tony Stark going to Oslo, Norway to keep Ultron from the internet and Captain America, Black Widow, and Hawkeye going to Seoul to stop Ultron as he attempted to upload his mind into the new body.

During the upload procedure, Scarlet Witch was able to read Ultron's mind, discovering his plan to destroy humanity. Before leaving Ultron, Scarlet Witch freed Cho from the Scepter's control, and Ultron killed the U-Gin employees and injured Cho. Captain America arrived and Cho warned him about the Cradle and the Infinity Stone used to create the body inside.

Battle
"You're no match for him, Cap." "Thanks, Barton."

- Hawkeye and Captain America

Hawkeye managed to locate Ultron in one of the trucks. Hawkeye suggested shooting it, but Captain America pointed out the possibility that the Infinity Stone inside Ultron's synthetic body could destroy the city. Rogers jumped on the truck, interrupting Ultron's download. Rogers decided to keep Ultron busy so that Hawkeye and Black Widow could retrieve the body. Rogers and Ultron fought, with Rogers doing his best to hold his own. At one point in the battle, Rogers lost his shield. Following the battle onboard a motorcycle, Black Widow was able to retrieve it for him. The fight eventually spilled into a moving train.

Meanwhile, Romanoff entered the truck; however, the Ultron Sentries lifted the truck into the air. On the train, Ultron almost defeated Rogers when Scarlet Witch and Quicksilver came to Rogers' aid. Ultron begged the twins not to turn against him, but Scarlet Witch pointed out that they had no choice. Ultron killed the conductor of the train and fled. This caused the train to speed out of control. Rogers had Quicksilver move civilians out of the way while Scarlet Witch used her powers to successfully stop the train. Romanoff managed to roll the Cradle into the Quinjet in midair, but she was kidnapped by Ultron in the process.

Aftermath
The Avengers managed to retrieve the Cradle, sending it back to the Avengers Tower for Bruce Banner and Tony Stark to examine it.

Ultron kidnapped Black Widow, and took her to Wolfgang von Strucker's HYDRA Research Base in Sokovia.

Scarlet Witch and Quicksilver managed to learn about Ultron's plan to eradicate all human life, so they defected from his side and join the Avengers to stop him.