He who knows how to guide a ruler in the path of Tao does not try to overide the world with force of arms.
It is in the nature of a military weapon to turn against its wielder.

Wherever armies are stationed, thorny bushes grow.
After a great war, bad years invariably follow.

What you want is to protect efficiently your own state, but not to aim at self-aggrandisement.

After you have attained your purpose,
you must not parade your sucess,
you must not boast of your ability,
you must not feel proud,
you must rather regret that you had not been able to prevent war.
You must never think of conquering others by force.

For to be over-deployed is to hasten decay,
And this is against Tao,
And what is against Tao will soon cease to be.

-Tao Teh Ching