In the first year of Tê Yu (1275) priest Mugaku (Bukko) had planted the banner of the dharma at Chênju temple in the province of T’ai Chou when the Mongols invaded China and overran the province. The teacher accordingly withdrew to Nêngjên temple in Wên Chou, but next year they came plundering into that province too. When one party of Mongol soldiers attacked Nêngjên temple, everyone fled except the teacher, who sat quietly in the main hall.
(The official) Ch’ên Kuo-hsiang often visited the master as a pupil. The teacher, pointing to the Mongol camp across the Wen river, said,
‘There is a rope across the river into the camp. Do you make trial of it.’ (Do you stop the fighting – Imai.)
Hsiang said: ‘How can I make trial of it?’
The teacher suddenly grabbed hold of Hsiang and slapped his face. Hsiang instantly had a realization, and made a bow.
This was first used as a koan subject in the interviews of Sei Seccho.