When Lord Arryn raised his banners in revolt, many of his bannermen sided with the King, chief among them Lord Randyll Grafton, who called the other loyalists to aid him in barring the rebels from entering the port of Gulltown. Eddard Stark decided to make his own way back to the North via the Fingers. Gulltown's defenses eventually fell, with Robert returning to Storm's End after slaying Lord Grafton. Both he and Eddard then called on their own bannermen.
Next House Tully joined the war on the rebels' side, following the marriage of Eddard and Jon to Catelyn and Lysa respectively, binding House Stark, Tully and Arryn together.[2] However, like in the Vale, not all the Tully bannermen joined the rebel cause. Houses Ryger, Darry, Goodbrook and Mooton took the side of the Targaryens in the war and Frey remained neutral until the situation became clearer.
After all the rebels were united, it was decided they would stand behind Robert, whose grandmother had been the daughter of King Aegon V Targaryen, giving him the best claim to the throne outside of Aerys, his children and grandchildren.
In turn, King Aerys summoned his own banners. All Targaryen bannermen responded, as did houses Tyrell and Martell who stayed loyal to the throne as did all of their bannermen, including Redwyne and Hightower. However, House Lannister, led by Tywin Lannister, who had recently resigned his post as Hand of the King ignored the summons, while House Greyjoy decided to remain neutral throughout the conflict.