War refers to the existence of an armed conflict or battle between nations, states, or independent sovereign entities, typically arising after a declaration of war. It is an act of military force wherein political opposition is carried out by rival military forces for the purpose of protecting or forcibly changing governmental policies and practices.
War is often viewed as a last resort and requires justification, which includes rules of engagement. From antiquity, war has been fought on tactical fronts and has always employed soldier or warriors in the act of fighting.
Wars are fought in campaigns, which are a succession of military operations. A war is considered to have been victorious if the opponent surrenders or if either party wins a majority of campaigns.