The Shield Islands, commonly called the Shields or Four Shields', are four islands of the Reach. They are located in the Sunset Sea west of Highgarden and protect the Mander river from theIron Islands. The islands include: Greenshield, ruled by House Chester; Greyshield, ruled by House Grimm; Oakenshield, ruled by House Hewett; and Southshield, ruled by House Serry.
When any sign of longships is spotted, elders in watchtowers light beacon fires, which in turn cause other watchtowers to light their own beacons and spread the warning to settlements further inland so they will not be caught unaware.
The Shields Islands were originally known as the Misty Islands. Two thousand years before the events of A Song of Ice and Fire the ironborn were free to sail up the Mander and plunder all the villages and towns all the way to Bitterbridge. Torgon Greyiron used Greyshield as his stronghold. King Joron I Blacktyde captured King Gyles II Gardener in a naval battle near the Misty Islands.
The Misty Islands were renamed the Shield Islands once King Garth VII Gardener drove out the ironmen and fortified them with men from the Reach. The Gardener Kings of the Reach armed the fisher folk of the Shield Islands to protect not only themselves, but also the river, thus giving the islands their name.
During Robert's Rebellion, longships of the Shield Islands were defeated by House Greyjoy in the battle at the Mander, although Lord Quellon Greyjoy was killed in the battle.
In 300 AC the Shield Islands are invaded by Ironborn, led by King Euron Greyjoy. The Ironborn fleet successfully outmaneuvers the local island defenses and captures most of their fleet. Euron Greyjoy names new Lords, Harras Harlaw is made Lord of Greyshield, Andrik the Unsmiling Lord of Southshield, Maron Volmark Lord of Greenshield, and Nute the Barber Lord of Oakenshield.
Soon after the retreat of Mace Tyrell's forces, he and Lord Paxter Redwyne converged on the Shield Islands to push back the Ironborn. Euron underestimated the swiftness of the Redwyne fleet and was caught in between Southshield and Oakenshield. After an intense battle called the Battle of the Shields between Redwyne and Ironborn ships, King Euron's flagship was destroyed leading to his death and ultimately the Shield Islands coming back under Reachman control.