6. Joffrey Executing Ned
While Catelyn's arrest of Tyrion might have started a war between the Starks and Lannisters, the execution of Ned Stark surely kicked the war into full gear. After Ned's failed coup to depose Joffrey as King of the Seven Kings and rightfully take his place as regent as willed by Robert, he is arrested and imprisoned in the dungeons of King's Landing. Varys convinces Ned to confess to treason in exchange for exile in the Night's Watch in order to ensure the safety of his daughters Sansa, whom the Lannister's hold hostage, and Arya, who has escaped. Ned does so but Joffrey ignores his mother's counsel that Ned be exiled, and instead orders his execution. Ned chooses not to protest in order to save his daughters and is killed. The move is a mistake by Joffrey for a number of reasons. Firstly, Ned was a man of his word and would have surely taken the black if it would ensure his daughters' safe return to Winterfell. Secondly, because of the fact that he had already sent word to Stannis about Jaime and Cersei's incestuous relationship and the illegitimacy of Joffrey, Tommen, and Myrcella, Ned would have dropped his own accusations against the Lannisters with the full knowledge that Stannis was sure to make his claim to the crown. Instead, Ned's death infuriates Robb and empowers his bannermen to name him King in the North and fires up his army to fight for the North's independence from the Iron Throne. Of course, as I mentioned before Joffrey could have been dead already had Ned told Robert the truth before he died. Just sayin'.