hào zhàn bì wáng, wàng zhàn bì wēi 好战必亡，忘战必危
Those Who Like to Go to War Will Perish; Those Who Forget War Will Be in Danger.
Those who are warmongering will inevitably be destroyed, and those who forget war will inevitably land in danger. That is, countries that like to make war are certain to bring destruction upon themselves, and countries which are not prepared for war will find themselves in dangerous situations. Haozhan (好战) refers to those who are keen to stir up conflicts and wars externally for their own interests and in disregard of moral principles; wangzhan (忘战) is to forget that war may befall oneself and thus fail to be appropriately prepared for it. Ancient Chinese believed that domestic and international affairs should be handled with a spirit of loving others. Wars exhaust a country’s resources and lead to loss of life; even a just war, a “war to end wars” conducted to defend a country and safeguard its people, should be a last resort. This phrase both illustrates the dialectical relationship between war and the rise and fall of countries and demonstrates the “civil” nature of the Chinese people who love peace.
Therefore though a country be powerful, if it is fond of war it will surely perish; though the land be at peace, those who forget war will inevitably be in danger. Hence even when there is peace throughout the land and the people lead settled lives, hunting is conducted in the spring and fall as military exercises. The vassal states train their troops and hold military drills in the spring and fall so that they do not forget war. (The General Commander’s Treatise on War)
To beanger is contrary to virtue, to wage war is an invitation of disaster, and fighting is the most unworthy action. Warmongers who seek victories in war always end in regret. (Sima Guang: History as a Mirror)