The Battle of Wu Fortress was the confrontation between two warrior groups, comprised of Thundering Rhino, Storming Ox, and Croc, and the Wu Sisters in the short Secrets of the Masters. The battle took place in the Wu Fortress at Hubei Volcano, in which the leopard sisters met their downfall due to the combined skills of Rhino, Ox, and Croc, who attacked their battle strength, making it their weakness and thus defeating the criminal trio.
A couple of days prior to the battle, the Wu Sisters escaped from their respective prisons and returned to their fortress. Once there, they sent messages to the leaders of all the Chinese Gangs, calling a meeting at their fortress in two days in order to form a criminal syndicate and take over China.
Meanwhile, Storming Ox, Croc and Thundering Rhino were tricked by Oogway to help defeat the Wu Sisters, in the tortoise's attempt to help them get out of lowly street fighting. During their journey to the fortress, Oogway stages his death, which leaves the trio demoralized. However, they decide to fight for honor after witnessing a village torn down by the Sisters and head back.
The meeting of the Wu Sisters and the gang leaders was interrupted by the arrival of the warriors Storming Ox, Croc and Thundering Rhino, who smashed through the wall and faced their foes. Recognizing the street fighters she had watched from her cell, Su Wu mockingly asked them how much the Imperial Army was paying them to arrest them. Rhino determinedly declared that they no longer fought for money and stomped on the ground with enough force to crack it. Intimidated, the gang leaders fled the scene (only to be captured by Oogway later). Furious that her plans to form a criminal syndicate had been foiled, Su Wu flung the meeting table aside and called her sisters to form the fiery vortex which made them so formidable.
The vortex flew around the room, knocking the trio backward before crashing into a pillar which fell on Rhino. As he struggled to keep it from crushing him, the vortex knocked the lone Ox sprawling and sent a hail of small rocks flying at Croc like bullets, sending him falling back next to his allies. Though they realized that it was hopeless fighting the sisters individually, Rhino pushed the pillar aside and declared that they could fight the enemy together.
And so as a team they leapt up into the air, dodging the vortex as it spun toward them. Rhino called on Ox to do his 'thing', and so Storming Ox swiftly analysed the vortex for weaknesses. Using his keen observation, Ox realized that the knot in the centre of the vortex, where the sisters were linked to each other by their tails, was the source of their power and they needed to be broken apart. Rhino was unable to get a clear shot as the sisters were spinning too fast, so Croc ran in and brought the vortex to a stop with his impenetrable hide. Though the intense friction began to burn Croc (according to him, his tail was on fire), he was able to adjust the vortex's position enough for Rhino to charge through the knot, effectively breaking the Wu Sisters apart.
Once separated, the Wu Sisters were no match for their foes: two of the sisters were swiftly subdued by Ox and Croc, leaving Su Wu to furiously fly at the warriors in a last stand. However, she too was sent flying into the head of a large statue. She landed in between her sisters as the statue head broke off at the jawline and landed on the sisters, trapping and defeating them.