Before the battle started, the original setup was a public hanging of dozens of pirates, many of whom were friends of Francis Bluehawk, Jack Swordmenace, and Nate Raidhawk. Oddly enough, Jack Swordmenace and Nate Raidhawk happened to be near the fort, porting at the docks and heard the cries of dozens of pirates, all singing the same song: Hoist the Colours. When the pirates checked the scene they found Captain Leon and other EITC about to hang several pirates at the noose in Fort Charles. Jack, Francis and Nate rallied the pirates, and together they rebelled against Leon. Gunshots were fired and Swordmenace was even stabbed in the chest by Jeremiah Dampswain, who at the time worked for Leon (You will often hear Jack making jokes about Jeremiah's weakness, as the sword got stuck and thus didn't kill Jack). The skirmish ended in the deaths of several EITC, many wounded, and two missing pirates, and is often regarded as the restart of the Pirate-EITC war, the new conflict now referred to as the 2nd 'Brethren Court War' (not to be confused with The 2nd Brethren Court itself).
All of the above events are true (This actually did happen, and in July: I was waiting for someone to post this.)