Engaging in armed struggle, whether between nations, races, cultures or other groupings, using various sized units in the air, at sea or on land. Combat between troops (as opposed to destruction of objects) is usually used to capture or retain important areas of territory (usually where rival claims for essential resources are involved); but it is also used to change or maintain political systems or leadership, to subject or free a people, or to prevent full-scale war.
Throughout the history of war the forms and methods of interpersonal combat have been altered, due to the development of weapons, organization of troops and the skill of military leadership. There is no way of determining the beginning of combat but the philosophy of war begins with "The Art of War" by Sun Tzu in the period of 400-320 BC. "To win one hundred victories in one hundred battles is not the acme of skill. To subdue the enemy without fighting is the acme of skill". The application of gunpowder to weapons in 14th century Europe changed the form of warfare from what was essentially groups of individuals in combat in a limited area using arrows, spears, lances and staves, to groups of units using smooth bore cannon and shotguns. The development of rifles in the 19th century increased the range, accuracy and speed of fire, causing extended formation tactics. With the invention of the aeroplane at the turn of the century and rockets during World War II, the effective range of battle was extended to the continental and intercontinental levels with the concomitant introduction of absolute war involving destruction of non-military targets and populations.
Combat between troops is an effective way to test the resolve of nations in conflict and the only way to defend against aggression and abuses of human rights, under which conditions warfare is justified. Defensive war is also always justified.
Certainly, war has not been rooted out of human affairs. As long as the danger of war remains and there is no competent and sufficiently powerful authority at the international level, governments cannot be denied the right to legitimate defense once every means of peaceful settlement has been exhausted. State authorities and others who share public responsibility have the duty to conduct such grave matters soberly and to protect the welfare of the people entrusted to their care. But it is one thing to undertake military action for the just defense of the people, and something else again to seek the subjugation of other nations. Nor, by the same token, does the mere fact that war has unhappily begun mean that all is fair between the warring parties. Those too who devote themselves to the military service of their country should regard themselves as the agents of security and freedom of peoples. As long as they fulfil this role properly, they are making a genuine contribution to the establishment of peace. (Second Vatican Council. Gaudium et Spes, 1965).
War inevitably leads to further war. It is barbaric and a criminal waste of human life. There is no justification for it.
There never was a good war, or a bad peace (Benjamin Franklin).
War is much too serious a matter to be entrusted to the military. (George Clemenceau).
The aim and result of war necessarily is not peace but victory, and any victory won by violence necessarily justifies the violence that won it and leads to further violence. If we are serious about innovation, must we not conclude that we need something new to replace our perpetual "war to end war?"