The 1587 siege of Ganjaku was part of Toyotomi Hideyoshi's campaign to seize Kyūshū during Japan's Sengoku period. While his half-brother attacked Taka castle on the island's east coast, Hideyoshi made his own initial landfall on the island's north coast, in Chikuzen province, and made his way towards Ganjaku castle, held by a retainer of Akizuki Tanezane.