九變篇 NO.2：

故將通于九變之利者，知用兵矣；
將不通九變之利，雖知地形，不能得地之利矣；
治兵不知九變之術(shù)，雖知五利，不能得人之用矣。

這句啥意思：

所以將帥精通“九變”的具體運(yùn)用，就是真懂得用兵了；
將帥不精通“九變”的具體運(yùn)用，就算熟悉地形，也不能得到地利。
指揮作戰(zhàn)如果不懂“九變”的方法，即使知道“五利”，也不能充分發(fā)揮部隊(duì)的戰(zhàn)斗力。

英文這么說：

The general who thoroughly understands the advantages that accompany variation of tactics knows how to handle his troops.
The general who does not understand these, may be well acquainted with the configuration of the country, yet he will not be able to turn his knowledge to practical account.
So, the student of war who is unversed in the art of war of varying his plans, even though he be acquainted with the Five Advantages, will fail to make the best use of his men.

“九變”是什么

“九變” 即今所謂作戰(zhàn)方式與策略原則之掌握運(yùn)用，當(dāng)據(jù)具體情況而高度靈活機(jī)動之意。本篇首先強(qiáng)調(diào)通于"九變"的重要，指出只有"通于九變"，才算"知用兵"。而要做到這一點(diǎn)，最重要的則是要從事物正反兩面的聯(lián)系中去考慮問題，即所謂"智者之慮，必雜于利害"，并以"利"為準(zhǔn)則，靈活地運(yùn)用作戰(zhàn)原則。