Throughout history, soldiers and scholars have sought to determine fundamental rules for the conduct of warfare. These approaches have been both prescriptive, stating what actions are allowed and forbidden in warfare, by law, ethics, or religion, and descriptive, analyzing the best practices and means by which a commander and his army or fleet can win a battle or a war.

Prescriptive principles of warfare

Ancient principles

The Book of Deuteronomy prescribes how the Israelite army was to fight, including dealing with plunder, enslavement of the enemy women and children and forbidding the destruction of fruit bearing trees.

Modern principles

The Hague and Geneva Conventions

See: Hague Conventions, Geneva Conventions

21st Century issues

There are several issues where appropriate the laws of land warfare are ambiguous or obsolescent. Among these are:

• The use of private contractors as soldiers or private armies and whether they are mercenaries or not under international conventions
• The status of persons detained by the U.S. in the War on Terrorism

In addition, several classes of weapons, such as land mines or cluster bombs, have been decried by non-governmental organizations and some governments as inherently inhumane. However, the United States has refused to denounce the use of these weapons. In the case of land mines, the U.S. position is that all U.S.-planted mines are clearly marked and mapped, and that all U.S.-planted mines can be deactivated by remote command. The People's Liberation Army also continues to use land mines.

Descriptive principles of warfare

Sun Tzu

Sun Tzu's The Art of War, written approximately in 400 B.C., listed five basic factors for a commander to consider:

• The Moral Law, or discipline and unity of command
• Heaven, or weather factors
• Earth, or the terrain
• The Commander;
• Method and discipline, which included logistics and supply

However, Sun Tzu implied individual initiative as a principle of warfare, stating "According as circumstances are favorable, one should modify one's plans."

Early Western theoreticians

Antoine Henri Jomini, in his book, Precis de l'Art de Guerre, in 1838, and Carl von Clausewitz, in his book Vom Kriege (On War) developed theories of warfare based on the experiences of the Napoleonic Wars. Jomini's approach was more theoretical than von Clausewitz'.

Modern NATO principles of warfare

The British historian J.F.C. Fuller developed a set of eight principles of warfare between 1912 and 1924:

• Objective
• Offensive Action
• Surprise
• Concentration
• Economy of Force
• Security
• Mobility and Cooperation

In 1994, the U.S. Army's Field Manual 100-5 listed the following basic principles:

• Objective: Direct every military operation toward a clearly defined, decisive and attainable objective. "The ultimate military purpose of war is the destruction of the enemy's armed forces and will to fight."
• Offensive: Seize, retain, and exploit the initiative.
• Mass: Mass the effects of overwhelming combat power at the decisive place and time.
• Economy of Force: Employ all combat power available in the most effective way possible; allocate minimum essential combat power to secondary efforts.
• Maneuver: Place the enemy in a position of disadvantage through the flexible application of combat power.
• Unity of Command: For every objective, seek unity of command and unity of effort.
• Security: Never permit the enemy to acquire unexpected advantage.
• Surprise: Strike the enemy at a time or place or in a manner for which he is unprepared.
• Simplicity: Prepare clear, uncomplicated plans and concise orders to ensure thorough understanding.

The British military adds to the above list:

• Maintenance of Morale
• Administration.

The Russian doctrine is similar, but includes the concept of Annihilation as well.