Arms control treaties and agreements are often seen as a way to avoid costly arms races which could prove counter-productive to national aims and future peace. Some are used as ways to stop the spread of certain military technologies (such as nuclear weaponry or missile technology) in return for assurances to potential developers that they will not be victims of those technologies. Additionally, some arms control agreements are entered to limit the damage done by warfare, especially to civilians and the environment, which is seen as bad for all participants regardless of who wins a war.
While arms control treaties are seen by many peace proponents as a key tool against war, by the participants, they are often seen as simply ways to limit the high costs of the development and building of weapons, and even reduce the costs associated with war itself. Arms control can even be a way of maintaining the viability of military action by limiting those weapons that would make war so costly and destructive as to make it no longer a viable tool for national policy.
Enforcement of arms control agreements has proven difficult over time. Most agreements rely on the continued desire of the participants to abide by the terms to remain effective. Usually, when a nation no longer desires to abide by the terms, they usually will seek to either covertly circumvent the terms or to simply end their participation in the treaty. This was seen in Washington Naval Treaty (and the subsequent London Naval Treaty), where most participants sought to work around the limitations, some more legitimately than others. The United States developed better technology to get better performance from their ships while still working within the weight limits, the United Kingdom exploited a loop-hole in the terms, the Italians misrepresented the weight of their vessels, and when up against the limits, Japan simply left the treaty. The nations which violated the terms of the treaty did not suffer great consequences for their actions. Within little more than a decade, the treaty was abandoned. The Geneva Protocol has lasted longer and been more successful at being respected, but still nations have violated it at will when they have felt the need. Enforcement has been haphazard, with measures more a matter of politics than adherence to the terms. This meant sanctions and other measures tended to be advocated against violators primarily by their natural political enemies, while violations have been ignored or given only token measures by their political allies.
More recent arms control treaties have included more stringent terms on enforcement of violations as well as verification. This last has been a major obstacle to effective enforcement, as violators often attempt to covertly circumvent the terms of the agreements. Verification is the process of determining whether or not a nation is complying with the terms of an agreement, and involves a combination of release of such information by participants as well as some way to allow participants to examine each other to verify that information. This often involves as much negotiation as the limits themselves, and in some cases questions of verification have led to the breakdown of treaty negotiations (for example, verification was cited as a major concern by opponents of the Comprehensive Test Ban Treaty, ultimately not ratified by the United States).
Nations may remain in a treaty while seeking to break the limits of that treaty as opposed to simply withdrawing from it. This is for two major reasons. To openly defy an agreement, even if one withdraws from it, often is seen in a bad light politically and can carry diplomatic repercussions. Additionally, if one remains in an agreement, competitors who are also participatory may be held to the limitations of the terms, while withdrawal releases your opponents to make the same developments you are making, limiting the advantage of that development.