A.o.A is a terrorist group in Digimon World 3 and Digimon World 2003. At first it is revealed that A.o.A did just bad things with Digimon, but later the player gets to know that A.o.A, led by Lord Megadeath, is trying to take over the world using the world-wide network. The A.o.A is using a Digimon called Vemmon to threaten the world. Vemmon can fuse with any machine, and A.o.A took the advantage of it. They stormed the military undersea base, MAGASTA, and launched the Juggernaut. Vemmon was transferred onto the Juggernaut and he fused with it, creating Destromon.
A.o.A's secret move is to turn every opponent into Oinkmon, by using their special configured weapons designed to absorb the target's matrix data. Amaterasu Server was completely taken over by the A.o.A, which means there are nothing but Oinkmon and A.o.A soldiers around. A.o.A also reprogrammed Knightmon to keep trespassers out of Amaterasu City. Though knowing of the fate of the A.o.A's opponents, some of the troopers actually began to hate their jobs. Needless to say, they kept it a secret together in the fear of turning into Oinkmon.
Back at the Vemmon project, Lord Megadeath himself, after Destromon shut down, used the other Vemmon clones to take control of the satellite Gunslinger. Right after Junior, the hero of Digimon World 3/Digimon World 2003 and his friends finally managed to turn the Oinkmon back into humans, the Gunslinger's Ragnarok Cannon was fired. It reached all the way to earth. Only Junior and some others were saved. The Ragnarok Cannon is designed to also absorb the matrix data; and turn anyone into Oinkmon. The people on earth were all absorbed, and Vemmon stormed the network. Everyone except Junior and some others were turned into Oinkmon.
Now with the matrix data stored in the satellite, Vemmon were all fused together and then mixed with the matrix data. The result was Snatchmon, a digivolved Vemmon. Snatchmon was supposed to be Lord Megadeath's partner, but Snatchmon just absorbed and destroyed him. Now, it was clearly the time for Junior to fight Snatchmon. Snatchmon refused to fight as himself. He offered Junior that he'd fight when he fuses with the Gunslinger and become Galacticmon. Now, it was time... and eventually, Galacticmon would combine with earth and become Gaiamon. But Junior defeated Galacticmon, and the Gunslinger fell on earth, in burning parts. All the matrix data was once again released, and now the A.o.A's terrorism was over.