War

War is an armed conflict between organized groups. These groups can be the military forces of entire states. They can also be armed groups under a specific command structure. Such groups must have the capacity to sustain military operations. War is often characterized by widespread violence and destruction. It also results in high rates of mortality. Most wars are fought to achieve specific objectives. These goals are usually political, economic, or territorial in nature.

Warfare refers to the specific activities and characteristics of different types of war. One extreme version is called total war. In total war, there are no limits on legitimate military targets. This type of warfare can lead to massive suffering for non-combatants. It also results in heavy civilian casualties. Combatants may demand significant sacrifices from their own civilian populations. This approach disregards the established laws of war.

There are many distinct categories of warfare used throughout history. Conventional warfare occurs between states without using nuclear or chemical weapons. In contrast, asymmetric warfare happens between groups with very different military capabilities. Some conflicts involve biological warfare, which uses infectious agents like bacteria or viruses. Chemical warfare uses weaponized chemicals, such as the poison gas used in World War I. This specific use of gas caused over one million casualties.

Other modern methods include cyberwarfare and information warfare. Cyberwarfare involves attacking a nation's information systems. Information warfare targets the networks that support power grids and transportation.

Historians and anthropologists study how war has changed over time. It is difficult to know if warfare was common in prehistory. Some experts believe early Paleolithic societies were egalitarian and peaceful. They suggest humans may have preferred trading and joint hunting. However, other researchers like Lawrence H. Keeley argue otherwise. Keeley suggests that 90% to 95% of known societies engaged in occasional warfare. He notes that early raids were often unorganized and lacked formal training.

As societies grew, the nature of conflict shifted. The Bronze Age saw an intensification of warfare with metal weapons like swords. Later, the invention of gunpowder caused major technological changes. A professor named Charles Tilly argued that war played a role in state formation. He stated that "war made the state, and the state made war." This means wars helped create states, which then continued to wage war. Since 1945, great power wars and territorial conquests have declined in frequency. However, civil wars have actually increased in absolute terms.

War aims are the desired benefits a group expects after a conflict. These aims can be tangible, such as acquiring new territory. They can also be intangible, like increasing a nation's reputation or prestige. Aims can be explicit, meaning they are published as policy. They can also be implicit, found in private discussions or memoranda. Some aims are positive, focusing on specific outcomes. Others are negative, intended to prevent an undesired result. These aims can even evolve into the conditions required for peace.

War has a massive impact on human populations. Conflict zones interrupt daily life and make travel difficult. The total number of deaths caused by war is hard to calculate. Estimates for historical deaths vary significantly among scholars. One scholar, William Eckhardt, calculated a low estimate of 151 million deaths. He based this on recorded battles and excluded unrecorded wars. Other researchers, like Ian Morris, provide much higher estimates. Morris suggests that up to 9 billion people may have died in wars throughout history. Despite these high numbers, advances in military medicine have helped decline battle deaths in recent years.