War has been defined in various ways. For present purposes, we may define was sustained sustained intergruop violence in which state military forces participate at least one side or on both sides in the case of interstate war and generally on only one side is the case of civil war. In a world of standing military forces it is hard to say exactly where peace ends and war begins. A military battle that is not sustained over time may or may not be considered a war. The brief Chinese-Soviet border clashes in March and July 1969, for example, entailed several small battles at a few points along the border, in which some hundred of people were killed. Similar ambigous is a long term violent struggle involving irregular forces, such as in Northern Ireland. There, uniformed British military forces waged a sustained violent struggle with a non state army, the Irish Republican Army (IRA), until a cease-fire that has held on and off since 1995.
Thus, many different activities are covered by the general term war. Consequently, it is not easy to say how many wars are going on in the world at the moment. Wars are very diverse. Several types of war tend to arise from different situations and play different types of roles in bargaining over conflicts. Starting from the largest wars, we may distinguish the following main categories.
Hegemonic War is a war over control of the entire world order – the rules of the international system as a whole, including the role of world hegemony. This class of wars is also known as global war, world war, general war or systemic war. The last hegemonic war was World War II.
Total War is warfare by one state waged to conquer and occupy another. The goal is to reach the capital city and force the surrender of the government, which can then be replaced with one of the victor's choosing. The 2003 Iraq War is a classic case. Napoleonic Wars, which introduced large-scale conscription and geared the entire French International economy toward the war effort. In total war, the entire society mobilized for the struggle, the entire society of the enemy is considered a legitimate target.
Limited War includes military actions carried out to gain some objective short of the surrender and occupation of the enemy. For instance, the US led war against Iraq in 1991 retook the territory of Kuwait but did not go on to Baghdad to topple Saddam Hussain's government. Many border wars have this character; after occupying the land it wants, a state may stop short and defend its gains.
Civil War refers to war between transactions within a state trying to create, or prevent, a new government for the entire state or some territorial part of it. The US Civil War of the 1860's is a good example of a secessionist civil war.
Guerrilla War which includes certain kinds of civil wars is a warfare without front lines. Irregular forces operate in the mid of and often hidden or protected by, civil populations. The purpose is not to directly confront an enemy army but rather to harass and punish it as as to gradually limit its operation and effectively liberate territory from its control.
In short, Wars are constantly taking place between states as well as in the states since theception of history itself. It will remain to the world exists because of various desires of individuals and state-actors as well.