Take Possible Chances For Impossible Advances

Seize The Opportunity To Lead A Sheep Away
Means that you always have to be alert and flexible to take any possible chances or opportunities. Then you always will gain advantages for advancing and that leads to victory.
While carrying out your plans be flexible enough to take advantage of any opportunity that presents itself, however small, and avail yourself of any profit, however slight.
Exploit any minor lapses on the enemy side, and seize every advantage to your side. Any negligence of the enemy must be turned into a benefit for you.
Yuan Dynasty China
During the final days of the Yuan dynasty, rebellion had broken out throughout the empire.
Initially there were several contenders vying to be the first to found a new dynasty on the imminent fall of the house of Yuan, but the field was narrowed to two; Chu Yuan-Chang and Chen Yifu.
The two armies met at Poyang Lake where a naval engagement was to take place. General Chen had the advantage of both troops and ships. His ships were large and sturdy and he had them lined up side to side across the entire expanse of the lake. He furthermore had the ships joined together with iron chains so as to create an impenetrable barrier. General Chu sent his ships to attack but they were defeated having failed to break through the cordon.
Fortunately for Chu the next day a violent northwest gale began to blow. Since Chen's flotilla was situated downwind, Chu took advantage of the situation to launch fireboats against the barrier. Soon Chen's troops were in a frenzy to save their ships from both the rising storm and the fire, which was fanned into a blazing fierceness by the wind.
Taking advantage of the panic and confusion that ensued, Chu launched his own fleet into the attack and they completely defeated Chen's forces. An arrow through his eye killed General Chen while general Chu became the founder of the Ming Dynasty.
In the year 770 BC, the duke of Zheng joined forces with Lu and Qi to attack Song.
The duke of Song was startled to learn of this and sought the advice of his ministers. Kong Jia suggested that they attack Zheng's old stronghold Yingyang. Zheng with few troops left, will be forced to return to save their state.
Kong Jia secured the help of the states of Wei and Cai to attack Zheng. Kong Jia suceeded and was about to march home when he decided that since they have to pass though Dai state, they could eliminate Dai in the name of borrowing a route.
Zheng soon recieved Dai's pleas for rescue. Zheng's reinforcement troops soon reached Dai, and the gates were opened to let them in. But the Zheng's forces captured and took over Dai instead. Thus, Song took the trouble to attack Dai but Zheng managed to reap the benefits.