Why states go to war

War does not determine who is right - only who is left. - Bertrand Russell It is traditional to distinguish nations from states, whereas a nation consists of an ethnic or cultural community, a state is a political entity with a high degree of sovereignty and territorial integrity.
A norm of territorial integrity spread rapidly across the globe in the twentieth century. While the successful acquisition of territory by force has become much less frequent, there have been numerous attempts to acquire territory by force during this time. We find many nations which are not fully sovereign as the degree of any state is a relative concept that depends upon the capacity and potential of its adversaries and contemporaries to harm.
The sense of nationalism merged in states arouses their capacity to not only compete but to seek power in order to subdue the contenders. Based on the fact that when states are capable, their intentions change overnight, the theory of classical realism believes that will to dominate is inherent in human nature. One of the proponents of classical realism theory, Kenneth Neal Waltz says that states' actions can often be explained by the pressures exerted on them by international competition, which limits and constrains their choices. This notion takes the idea of state security and defence far ahead that being required.
Although states must act in a way that ensures their security or any risk falling behind on its sovereignty. But living in an anarchical world if the sovereignty of any state is at stake, then the pursuit for the armament or towards arms race to achieve an optimum level of defence vis-à-vis its adversary is the only option available. A realist prioritises national interest and national security. A classical realism puts human nature, or the urge to dominate, at the center of its explanation for war. The states go for war as this theory explains only general principles of behaviour that govern relations between states in an anarchic international system, rather than specific actions. These recurring principles of behaviour include balancing of power; the theory was revised by Stephan Walt, modifying the "balance of power" concept to "balance of threat", entering into individually sub-optimal arms races, and exercising restraint in proportion to relative power.
If the production of armaments ensures security then why states go for war after acquiring nuclear weapons. The functioning deterrence thought to achieve peace and no-war situation but wars are still experienced in the international system. The development of nuclear weapons opened up the option of limited war although the chances of escalation to the nuclear ladder cannot be ruled out.
The example of India-Pakistan relations in historical perspective reveals that when Pakistan acquired nuclear power status and maintained the balance of power in the region even then it went for war on Kargil, (the Kargil Conflict between Pakistan and India took place in Kashmir between May and July 1999) the objective of the whole conflict was to cut off the link between Kashmir and Ladakh by hitting National Highway No 1 (NH 1) and cause Indian forces to withdraw from the Siachen Glacier forcing India to negotiate and resolve the decade old Kashmir dispute.
The element of political leadership is significant in determining states' posture for going into war. The rationality of the decision-maker between the conflicting parties is usually difficult to achieve on practical grounds that sows the seeds for war situation. The hawkish and hardliner leaders design wars under the curb of national interests, the Bush administrations' mindset was more war prone than Obama. Similarly Israeli hardliner PM Benjamin Netanyahu believes in power politics through war manifestation than by other means.
The events since September 11, 2001 have aggravated the global imbalance in terms of political and military power. Pakistan is a key US ally in the War on Terror and has long complained that India's nuclear deal, agreed in 2005, will upset the strategic balance of South Asia by endorsing it as a nuclear weapons state. Pakistan must fulfil its assurances that it will not permit any territory under its control to be used to support terrorism in any manner. The non-state actors is an eminent threat to international community and that results into the' global war on terror. Although wars are waged to remove obstacles to harmony but the fact still persists that 'wars do not win peace.