《六韬·武韬·文伐》
这就是所谓上察天时，下观地利，有利的征兆一旦出现，就可以兴师讨伐敌国了。 
所谓上察天，下察地，征已见，乃伐之。 
This is the so-called observing the weather and observing the geographical advantage. Once the favorable sign appears, you can send an army to attack the enemy country.