|“|| Storming Ox: What's in the box, Shen?|
Shen: Well, you see, it's a gift. It's your parting gift, in that it'll part you; part of you here, part of you there, and part of you way over there staining the wall!
Storming Ox: You insolent fool!
|—The beginning of the battle, Kung Fu Panda 2|
The Invasion of Gongmen City was the return of Shen to his former home in Gongmen City after having been banished by his parents. Shen's return with his army and new weapon triggered a short battle that resulted in the death of the Kung Fu Council's leader, Master Thundering Rhino, and the surrender of Masters Storming Ox and Croc. This ultimately placed Shen in complete control of the city.
One afternoon, Masters Storming Ox and Croc were sparring in the palace courtyard, tutored by Master Thundering Rhino and observed by the Soothsayer. They were unaware that just outside the palace gates, Lord Shen was slowly approaching his former home after years of exile.
Shen effortlessly dispatched the antelope guards in front of the gates and then sliced through the gate bar, slamming open the doors. Shen walked inside and approached the Kung Fu Council and the Soothsayer, who were all astonished to see the exiled lord after so long. After a brief but tense exchange between himself and the Soothsayer, Shen casually confronted the masters, telling them he was there to take back what was his; Gongmen City. The warriors made it clear that they would protect the city no matter what, which surprisingly pleased Shen as a gang of his wolf soldiers pushed a large box into the yard. When Master Storming Ox inquired as to what was in the box, Shen explained that it was a parting gift of sorts... in that it would literally part them.
Enraged, Storming Ox leapt at the peacock, but Shen countered by lassoing Ox's horn with a rope, pulling him to the ground. Croc immediately leapt into the fray but was knocked away by Shen and barely managed to deflect Shen's throwing knives with his sword. In the skirmish that followed, Shen easily out fought Masters Storming Ox and Croc, knocking them sprawling and stunning them, but was met with stronger competition from Master Thundering Rhino, who deflected several of Shen's blades using his Cloud Hammer and his horn, slowly approaching him as he did so. He eventually pushed the peacock back with a thrust of his hammer and destroyed the remainder of his knives. Thundering Rhino declared that this defeat was a warning, and that Shen was no match for their kung fu.
Shen, however, was prepared for this, and unveiled the object inside the wooden box... a cannon. Thundering Rhino prepared for battle, but was no match for Shen's device and was killed a second after Shen lit the fuse. With Thundering Rhino dead, Shen threatened to turn his cannon on the city unless Storming Ox and Croc surrendered. He had the two masters imprisoned in Gongmen Jail and planted Master Rhino's Cloud Hammer in his courtyard as a trophy.
The kung fu masters of Jade Palace would soon learn of Thundering Rhino's death, and set out to stop Shen and his weapon.