"What with two - no, three, wars...though I'm not sure you could call that third one a war - and nearly two decades of animosity between us, our families certainly aren't friends."
Tyrion Lannister mentions the War of the Three Banners in a conversation with Eyron Morvayn.[src]

The War of the Three Banners (also known as the Three Banners War) was a brief, non-causality conflict in the history of the Borderlands, fought between the "three banners": House Blackgard, House Lannister and House Martell. The war erupted after House Blackgard was accused of stealing money from both the Lannisters and the Martells. The war ended with the inconclusive Battle of Blackgard, where House Lannister surrendered and House Martell signed a fragile alliance with the Blackgards.