 Those who met these standards earned an exemption from corvée labor and taxes for their entire family.The "Huainanzi" advises its readers not to use crossbows in marshland where the surface is soft and it is hard to arm the crossbow with the foot.The "Records of the Grand Historian", completed in 94 BC, mentions that Sun Bin defeated Pang Juan by ambushing him with a body of crossbowmen at the Battle of Maling.