Being unconquerable lies with yourself; being conquerable lies with your enemy.
Quickness is the essence of the war.
Without local guides, your enemy employs the land as a weapon against you.
Without subtle ingenuity of mind, one cannot make certain of the truth of their reports.
Weak leadership can wreck the soundest strategy; forceful execution of even a poor plan can often bring victory.
An army may be likened to water, for just as flowing water avoids the heights and hastens to the lowlands, so an army avoids strength and strikes weakness.