War of the Five Kings

The War of the Four Kings is a major military conflict that erupted in the wake of the death of King Robert Baratheon. His son Joffrey took the Iron Throne, but it was claimed that Joffrey was a bastard born of incest between Queen Cersei and her twin brother, Ser Jaime Lannister. On this basis, Robert's younger brother Stannis Baratheon also claimed the throne. Robert's youngest brother, Renly Baratheon, also claimed the throne, claiming that he would make a superior ruler to the ruthless, unpopular Stannis.

The situation was complicated further when Robb Stark of Winterfell, leading a host south to relieve a Lannister attack on the Riverlands, was declared the King in the North by his lords bannermen (and some of the river lords), and he declared the North to be a sovereign state no longer subject to the rule of King's Landing.