Kant

Kantian ethics state the good moral law is unconditionally and universally binding. Kantian theory focuses on the motives of an act. By applying the Kantian ethics to use of weapon, it becomes clearly and dimensional: ‘to protect one’s life is duty’. One could use weapon only if one’s life is threatened. Thus the purpose of weapon is to used to offence enemies or defend self. If the role is country, ‘to protect countries’ security is duty’

In the modern time, only when the weapons are used for self-defending is treated moral. So for example, does the use of massively destructive weapon morally accepted, could be analysis by this maxim, instead of judging from consequence of the war.  

Finally, the use of weapon should also be responsible when it is invented. This approach argues the immorality happen when we treat others as only means to meet our needs. To test the biological or chemical weapon, the lives (mankind, animals) are scarified to meet the scientist own purposes. In this case, scientists are failed to obey the Kant ethics.

Kantian Ethics

Analysing the social and ethical implications of military development

Military Technology Out of Control?