During the night of 26 August, the Japanese crossed the Toa-to-kei river under cover of darkness, and at dawn on 27 August separate Japanese columns made a surprise attack on the Bagua battery and Changhua. In a short and sharp early morning engagement generally known as the Battle of Baguashan, the Japanese stormed the Bagua battery and occupied Changhua. The Formosans suffered heavy casualties in this battle, and two of their commanders, Wu Tang-hsing (吳湯興) and Wu Peng-nien (吳彭年), were killed. The Formosan forces fell back to Chiayi and Lu-kang. The battle of Baguashan, the largest pitched battle ever fought on Taiwanese soil, was the decisive engagement of the invasion, and its loss doomed the Formosan Republic to early defeat. Subsequent engagements merely postponed the end.