The Battle of Sokovia was a major battle between the Avengers and Ultron in Novi Grad, Sokovia. Convinced that humanity was the greatest threat to peace on Earth, Ultron planned to commit global genocide by creating a device that would lift a section of Novi Grad skyward and cause it to recreate a meteoric impact when it crashed into the Earth. However, the Avengers' actions resulted in the threat being neutralised and the Ultron Offensive being brought an end.

Background

During an attempt to create a more powerful body, Ultron attacked the U-GIN Genetic Research Facility and manipulated Helen Cho to use a machine for the creation of his new body. Under the control of the Scepter, she used a machine called the Cradle to create the body.

Then, Scarlet Witch, receiving a vision about the global destruction Ultron would create, freed Helen Cho from the mind control. Ultron attacked them, but in the end Scarlet Witch escaped with Quicksilver along with Dr. Cho; however, Cho was severely wounded by Ultron.

Minutes after, Captain America talked with the injured Cho and discovered Ultron's plan. With the help of Hawkeye in a Quinjet, Captain America pursued a U-GIN Truck, because the body could be the key to destroying Ultron. 

Black Widow, through some clever planning, managed to retrieve the body, but was captured by Ultron in the process. After a battle in the streets of Seoul, the machine was taken to Avengers Tower. Bruce Banner and Tony Stark began to work and created a new A.I. for the body, but Stark discovered that J.A.R.V.I.S. was alive. Due to that, he decided to transfer the A.I. into the body.

Captain America, Scarlet Witch, and Quicksilver arrived to try and stop them, leading to a brawl until Thor arrived, providing the Cradle electrical power in order to awaken the A. I. being.