The fight was caused when there were speculations that the Black Hood was from the Southside of town. With the differences between the Northside and the Southside, this made matters worse, causing both sides of town to be more divided than ever before.
Triggering the Feud
After suspecting that the Black Hood was from the Southside of town, as statistics had shown that his victims were or at one point were residents on the north side of Riverdale, Archie wanted to intimidate the killer by trying to call him out, his motive being that he wanted to attract the dangerous killer to come for him so that he could single-handedly kill him. Having loaded up with guns at the local army-navy store, he carried out his plan on the Southside, as he maneuvered through the streets tagging buildings with a spray-painted Red Circle logo. However, he was caught by a group of young Serpents, and they weren't pleased to find him tagging their turf. Sweet Pea and his gang took offense to his mark as a message towards them. Later, taking a second look at his mark, he realized that it's a message towards the Black Hood.
The two boys had a brief conversation with each other, as Sweet Pea informed Archie that he was on the wrong side of town. He advised Archie to get his ass back on the Northside of town, before someone got hurt. Which Archie later retaliated, by telling Sweet Pea to get out of his way, "or someone will get hurt". This enrages Sweet Pea, to which he then pulled out a knife on Archie, expecting him to be scared and run away. However, he was caught off guard along with the rest of the Serpents, when Archie pulled out a gun pointed towards him, yelling, "WHO MADE A MISTAKE, WHO MADE A MISTAKE?", causing the Serpents to retreat.
Trouble Arrives at the Front Door
Later, at the Andrews house, after Archie and Veronica had a serious talk about Archie owning a gun, they heard a knock on the front door. As Veronica was approaching the door to open it, with Archie a bit on edge, as he kind of suspected that it would be the Serpents. However, when Veronica opened the front door, it was Reggie and Dilton Doiley, along with the rest of the Bulldogs behind them, who came unannounced, bringing a few boxes of Pizza's over by his house. Reggie expressed his gratitude to Archie for not exposing him as the owner of the hood mask that Mr. Weatherbee found in Archie's locker. In "the book of Reg", that made him a top-tier loyal badass. He also had other news; he and the guys were talking earlier and came to the decision that if he wanted to keep "The Red Circle" going, they were in.
However, their decision was interrupted when Veronica heard engines revving outside of Archie's house, to later find a group of Serpents arriving at the front of Archie's house, approaching his front door. Not long after, Veronica warned Archie that trouble had arrived. Archie approached the door to find Sweet Pea and his gang, stating that they were there for payback concerning their last encounter. Reggie arrived at the door, backing Archie up. Veronica decided that if they were to fight head-on, rules must be placed, and the first rule was no weapons in the fight that was to ensue.
Serpents VS. The Red Circle
Serpents and the Bulldogs stood on their respective sides in the rain, preparing for the fight. After more members arrived on either side, Archie and Sweet Pea were in a standoff. Initiating the fight, Archie walked slowly towards him, looked Sweet Pea straight in the face, and took the first punch, declaring war. Both sides of ran forward attacking each other. As the two sides fought, Archie spotted Dilton pulling out a pocket knife and was thrown down towards the ground not long after, by Sweet Pea. Before Sweet Pea could continue, Veronica intervened by firing Archie's gun into the air, which ended the fight, with the Serpents retreating. However, the Red Circle did not make it out unscathed, as Dilton was stabbed in the leg, and had to be rushed away by Reggie to the hospital. Nevertheless, Dilton knew what was required of him, he had to make up a cover story; he would say that he was walking when he was ambushed by Serpents who stabbed for no apparent reason.