There are many reasons both for and against a declaration of war to resolve an opposing conflict. Though there are many different types of warfare, an aggressive means can be considered a just cause. However, in many cases, affirmative action cannot be a warranted solution. War is a delicate instrument of peace, not a ravaging hammer of conquest. .
In one instance, I believe that war can be declared on a common threat to the majority. Though we all have different cultures and beliefs, we have the right to defend that individuality from oppression or extinction. If an aggressor jeopardizes this right to exist, then war is definitely an ethical solution. Too many cultures in history have fallen to this fate, leaving us now, only to guess at its purpose or place. .
To discontinue the production of biological weapons and devices of mass devastation is also a basis for a declaration of war. Their sole purpose is to destroy a specific area or in some cases, entire countries. It poses a serious threat to the entire planet due to the hazards in it's nature, range, construction, and use. I find no plausible reason why anyone should have access to those kinds of devices.
Another rationale for an assertion of conflict is to aid those who cannot protect themselves from would-be aggressors. To defend others by war not only preserves their culture and individuality, but in the end, creates a potential friendship for trade and economy value. It also, in essence, establishes the hope of peace, even if it's on the other side of war.
If a people is starving, suffering, or being tortured due to an uncompromising government or radical means, then it is conceivable that war is an ethical option. It is unprincipled for any position of power to use fear or torment for control or wealth. If this is the case, then a call for aid is necessary and a duty to assist is essential. I believe that in this instance, the use of war is necessary, even if it is just to remove one bad element.
