The Battle of Kashii (樫井の戦い) was the very first battle of the Summer Campaign of the 1615 Siege of Osaka

Siege of Osaka

The was a series of battles undertaken by the Tokugawa shogunate against the Toyotomi clan, and ending in that clan's destruction. Divided into two stages , and lasting from 1614 to 1615, the siege put an end to the last major armed opposition to the shogunate's establishment...

. As the Shogun's Eastern Army prepared to renew the siege begun the previous winter, the Ōsaka

Osaka Castle

is a Japanese castle in Chūō-ku, Osaka, Japan.Originally called Ozakajō, it is one of Japan's most famous castles, and played a major role in the unification of Japan during the sixteenth century of the Azuchi-Momoyama period.-Description:...

 garrison sallied forth, ambushing Tokugawa forces in a number of skirmishes and sieges. In the battle of Kashii, a contingent of forces loyal to Toyotomi Hideyori

Toyotomi Hideyori

was the son and designated successor of Toyotomi Hideyoshi, the general who first united all of Japan. His mother, Yodo-dono, was the niece of Oda Nobunaga....

, lord of Ōsaka, attempted to siege Wakayama Castle

Wakayama Castle

' in Wakayama, Wakayama Prefecture, Japan, sits at the mouth of the Kii River. Originally Ōta castle, home of the Saiga Ikki, it was captured by Toyotomi Hideyoshi in 1585, during the Siege of Negoroji; many monks from Negoroji sought refuge in Ōta, which was soon destroyed by flood...

, which was controlled by Asano Nagaakira

Asano Nagaakira

was a Japanese samurai of the early Edo period who served as daimyō of the Wakayama domain, and was later transferred to the Hiroshima Domain.Born Asano Iwamatsu, he was the son of Asano Nagamasa, who was a senior retainer of Toyotomi Hideyoshi. In 1594, Nagaakira was made a retainer of Toyotomi...

, an ally of the shogun. The attackers were led by Ōno Harunaga

Ono Harunaga

was a general under Toyotomi Hideyori, and fought in the Siege of Osaka in 1615. He had become lord of Osaka castle after the battle of Sekigahara. Ono led forces against those of Wakayama Castle in the battle of Kashii and in the battle of Tennoji, where he was killed in...

, Hanawa Naoyuki, and Okabe Noritsuna.

Asano's garrison realized that their attackers were far from support or reinforcements, and met them in battle at Kashii, a short distance from Wakayama. Okabe and Hanawa were killed in the battle, and Ōno was therefore forced to retreat back to Ōsaka.