Following the legendary fight where Garp and Roger defeated Rocks D. Xebec, Dragon faced serious consequences. During the chaos, the young Marine disobeyed direct orders to protect civilians, saved Shanks and Shamrock, and even neutralized a World Noble in order to protect Kuma.
To the World Government, these were unforgivable crimes.
Dragon was arrested — and the world assumed that Garp turned his back on him.

But history took an unexpected turn: Garp visited Dragon in prison, made his defining decision, and broke him out. It was the moment that transformed Dragon from a disillusioned Marine into the man who would later establish the Revolutionary Army.
Ironically, the organization that now shakes the World Government every day only exists because Garp gave Dragon the chance to fight for his own justice.