After Ishida Mitsunari was defeated at the Battle of Sekigahara in 1601, Tokugawa Ieyasu appointed his general Ii Naomasa as daimyō of a new domain centered at Sawayama Castle.

[2] Ii Naomasa was one of the most capable and trusted of Ieyasu's generals, noted not only for his military prowess, but also for his diplomacy and strategies.

Therefore, Ii Naomasa decide to relocate his seat to a new location on the shores of Lake Biwa, constructing a new castle per the latest contemporary design.

[3] Hikone Castle consists of two concentric water moats surrounding a 100 meter hill called "Mount Konki".

[2] To save time and expense, the Ii clan scavenged many stones and buildings by demolishing all other fortifications in their territory and bringing the materials to Hikone.

Often considered the foremost of the fudai daimyō, the Ii clan served in many important positions within the Tokugawa shogunate.

During the Bakumatsu period, the tairō Ii Naosuke was virtual ruler of the country during a time of very weak and ineffectual shoguns.

However, his acquiescence in ending Japan's national isolation policy under pressure from the western powers led to his assassination by pro-Sonnō Jōi forces in 1860.

During the Battle of Toba-Fushimi, although Hikone forces were stationed at Osaka Castle, they did not join the shogunal army, but simply marched home.

When the new government ordered the dismantling of all feudal-era fortification nationwide, Hikone Castle was spared by a direct request from the emperor himself, who was touring the area.