The Battle of Wakanda was an open confrontation that pitted the Avengers, the Guardians of the Galaxy, the Wakandan armies and their allies against the Outriders, the remaining members of the Black Order, and eventually, Thanos himself.
On his quest to obtain the six Infinity Stones, Thanos stole the Space Stone from the Asgardian refugee vessel Statesman. As Hulk was sent to Earth via the Bifrost to warn of Thanos' coming, the Titan tasked his four Children to obtain the Mind and Time Stones from the planet. To achieve this task, the Children split up, with Proxima Midnight and Corvus Glaive leaving to retrieve the Mind Stone from the forehead of the android Vision.
The Children ambushed Vision and his lover Wanda Maximoffin Edinburgh, heavily crippling the Avenger. However, their attempt to retrieve the Stone was thwarted by the rogue Avengers, Steve Rogers, Black Widow and Falcon, who were warned of the threat by the returning Bruce Banner. With Glaive heavily injured, the Children were forced to retreat in their Q-Ship back into space to nurse their wounds.
Reuniting with War Machine and Banner in the New Avengers Facility, the Avengers considered their next move, knowing that Midnight and Glaive would eventually return.
Having analysed the Stone's properties, Vision proposed having Maximoff destroy the Stone using her abilities, volunteering to sacrifice himself to prevent it falling into Thanos' hands. Unwilling to kill their friend, Banner proposed the difficult task of removing the Stone from Vision to safely destroy it without needlessly taking Vision's life. Rogers suggested taking Vision to Wakanda, the only nation on Earth with the resources capable of achieving this.
Notifying the Wakandan King T'Challa of their intentions and the threat of Thanos, he and the General of the Dora Milaje, Okoye, began to mobilise Wakanda's armies in preparation for the assault. Recruiting Rogers' old friend and the White Wolf, Bucky Barnes to the cause, T'Challa and Okoye greeted the arriving Avengers, where Rogers reunited with Barnes.
The Avengers took Vision to the lab of T'Challa's sister, Shuri, who prepared to undergo the time-consuming process of removing the Stone. However, at that moment, disturbances were detected in the upper atmosphere above Wakanda - the enemy had returned. Sent by a Q-Ship, alien dropships began descending from the sky above the city. Though the city's energy dome prevented them landing directly in the city, five dropships landed on the outskirts of the dome.
Elsewhere in space, Thor was rescued from the ruins of the Statesman by the Guardians of the Galaxy. Setting out on a separate quest to stop Thanos, Thor, Rocket Raccoon and Groot made for the Dwarven star forge of Nidavellir to forge a weapon powerful enough to kill Thanos. However, upon arrival, they found the Realm devastated, the forge extinguished, and the Dwarves massacred. Only the Dwarf King, Eitri, remained, who explained that he was forced by Thanos to forge the Infinity Gauntlet to harness the power of the Infinity Stones, before being crippled and forced to watch his people executed.
Together with Eitri, Thor and Rocket worked to repair and restart Nidavellir, in order to forge Stormbreaker, a powerful axe capable of killing Thanos and summoning the Bifrost. However, the iris mechanism focusing the star's energy, required to heat the Uru metal ingots for the weapon, was crippled. Volunteering to physically hold the iris doors open, Thor bore the full brunt of the star's power to light the forge and allow Eitri to heat the metal and pour it into the mould.
However, the critically injured Thor fell unconscious partway through the process, shutting the iris and leaving the weapon incomplete and without a handle. With the complete Stormbreaker the only thing that could heal Thor, Eitri frantically searched for a handle, calling for Groot to help. Steeling himself, the Guardian stepped up, using his own wooden arm instead as an improvised handle, completing Stormbreaker.
Back in Wakanda, in order to buy time for Shuri to remove the Mind Stone from Vision, T'Challa ordered the city to be evacuated, the preparation of the city's defenses, and for Rogers to be given new vibranium shields.
While Maximoff remained in Shuri's lab with Vision to destroy the Stone the moment the process was complete, the rest of Rogers' team, with Bruce Banner using a Hulkbuster armor, prepared for battle.
Leaving to face the dropships, the Avengers joined T'Challa, Barnes, the Dora Milaje, Wakanda's King's Guard, the Jabari Tribe, and the remainder of the Border Tribe at the outskirts of the city, preparing to face Thanos' army.