| In military terms, the pre-emptive strike is a method of the defensive use of force, the deployment of military power to prevent an attack by another state and minimize danger to yourself if you are attacked. There are two possibilities for striking first -- the pre-emptive strike and the preventive strike, the difference being an issue of timing as states attempt to determine when the adversary will attack.
A pre-emptive strike is a matter of hours, days, or weeks, and it occurs when there is belief in an imminent attack. It follows the maxim that "the best defense is a good offense." Examples of pre-emptive strikes include the Japanese bombing of the United States' Pearl Harbor in World War II and Israel's strikes on Egypt in the Six Day War of 1967.
A preventive strike, on the other hand, deals with months or years, a long term strategy. A state believes the attack is inevitable, but not imminent. An example of this is the Maginot line used by the French in World War II. | 
