The following outline is provided as an overview of and topical guide to war:
War - organised and often prolonged armed conflict that is carried out by states and/or non-state actors - is characterised by extreme violence, social disruption, and economic destruction. War should be understood as an actual, intentional and widespread armed conflict between political communities, and therefore is defined as a form of political violence or intervention.
An absence of war is peace.
See: Warfare by era, above
Types of military operations, by scope:
Philosophy of war - examines war beyond the typical questions of weaponry and strategy, inquiring into such things as the meaning and etiology of war, the relationship between war and human nature, and the ethics of war.