War has been a permanent part of human history. Whether it is natural to the human race is a debate better left to the anthropologists and philosophers, but certainly it has rarely been absent from Europe since the continent's recorded history began with the Greeks. War can be defined as the state of organized, socially approved, and regulated violence by one clearly defined group of people against another. This definition covers both primitive and civilized societies; it includes civil wars but excludes the opening phases of revolutions (which often become civil wars) and modern terrorism. A society gives a war its approval by defining it as a just war and by continuing to follow the leaders who direct the war effort, although there is often a substantial minority opposed to the war. When a large enough portion of a people become opposed to a war, it will probably end either through a unilateral withdrawal of troops or an overthrow of the leaders responsible.
The violence of war has always been carefully regulated either by codes of conduct or by law. Some armies and eras have been more rigorous than others in limiting what has and has not been permitted in war, but there have always been limits of some sort. Codes of chivalry, religious tenets, and international law have at different times dictated the controls on wartime violence. Those who transgress the limits of their societies have usually been quickly and severely punished, often by summary execution.
Army is the common term for the organized group of men who engage in war. Historically women rarely have participated directly in war, except when their states or societies were in dire emergency. The participants must carry weapons of some sort, have the rudiments of a command system, and have enough of a sense of discipline to act more or less as a unit in battle. In regard to weapons, there have been in history only two types: shock and missile. Shock weapons arc those held in the hand when contact with the enemy's body takes place; their use is known as hand-to-hand combat. Missile weapons involve shooting projectiles of some sort at the enemy. Artillery is simply a special category of missile weaponry that depends on machines or large-caliber guns to launch projectiles heavier than those individual men can propel. Some weapons have functioned as both