In military science, defense (or defence) is the art of preventing an attack, or minimizing the damage of an attack, e.g. by preventing an enemy from conquering territory.

Thus, if a party attacks an enemy who is about to attack that party, this could be called defense. However, this leaves room for interpretation.

Typically defensive are e.g. armor and a bunker. Also defensive are guns, rockets, etc. with a range within the defenders territory: they can only attack an attacker. If the weapon is mobile it may also be used in an attack, after moving it.

Defense may also be a euphemism for war, such as Ministry or Department of Defense, although this does not carry the negative connotation of war. Usage in this way has broadened the term to include most military issues.

Territorial defense

In the strictest sense of the word, military defense means the protection of a territory against an enemy. After the emergence of the nation-state as the main international actor, the military is usually organised on national level, and territorial defense is synonymous with national defense.

Modern collective defense arrangements are changing some of these traditional views. During the Cold War, the defense of most countries was dominated either by the United States or by the Soviet Union. Most Western European countries were organised within NATO, while most Eastern European countries were united within the Warsaw Pact.

Defense through the ages

Historically, it was generally true that defenders had an advantage over attackers. Battles commonly focused on sieges of important cities, allowing defenders to strengthen their position. They had the ability to make preparations for the battle to protect themselves from the enemy while making the enemy vulnerable, such as preparing positions such as trenches and fortifications or in more modern time laying obstacles such as land mines. However in encounters larger than the small scale the attacker may often have the advantage, since they get to choose the time and place of battle. An attacker may concentrate their entire force on a small part of the defended area, while the defender is forced to spread their forces over the possible area of attack.

In the modern era the defenders' advantage has been gradually reduced, due to factors like the increased mobility of the modern forces, better communication technology and increased destructiveness of weaponry (destroying most defense-based structures with ease).

See also

• Arms trade
• Defense contractor
• List of United States defense contractors
• Military-industrial complex
• Private defense agency
• Self defense
• Defensive war
• Missile defense
• Department of Defense