http://mabufs.i2p/goon-fu/chinese-origins-japanese-ninjutsu
And when the enemy, having believed the peace assurances, let his guard down and became less cautious, the enemy undertook a decisive military operation. The plot was thus exposed, and the ambassador, who had been in the enemy camp for cover, was put to death. The Chinese chronicles describe an incident that happened during the struggle of the Han emperor Gao-tszu (206-195 BC) with the Qi princedom.