no plan survives contact with the enemy

no plan survives contact with the enemy

Military plans always need to be changed once they are enacted in real-life military situations. The saying emphasizes the need for flexibility, as opposed to strict adherence to strategy. It is attributed to Helmuth von Moltke the Elder, a 19th-century Prussian field marshal. Men, be ready to make changes on the battlefield—we all know that no plan survives contact with the enemy.
See also: contact, enemy, plan, survive