The route to Tokyo was via Kumamoto, the site of a historic castle, and the primary garrison town for the Imperial Japanese Army in Kyūshū.

Kumamoto castle, built in 1467, was among the strongest in Japan, Saigō was confident that his forces would be more than a match for Tani's peasant conscripts, who were still demoralized by the recent Shinpūren Rebellion.

After two days of fruitless attack, the Satsuma forces dug into the rock-hard icy ground around the castle and tried to starve the garrison out in a siege.

The situation grew especially desperate for the defenders as their stores of food and ammunition had been depleted by a warehouse fire shortly before the rebellion began.

The defeat of Saigō at Kumamoto greatly demoralized and weakened his forces, who retreated in disarray and were unable to resume their offensive.