The relation or union between persons or families contracted by intermarriage. In international law. A union or association of two or more states or nations, formed by league or treaty, for the joint prosecution of a war, or for their mutual assistance and protection in repelling hostile attacks. The league or treaty by which the association is formed. The act of confederating, by league or treaty, for the purposes mentioned. If the alliance is formed for the purpose of mutual aid in the prosecution of a war against a common enemy, it is called an "offensive" alliance. If it contemplates only the rendition of aid and protection in resisting the assault of a hostile power, it is called a "defensive" alliance. If it combines both these features, it is denominated an alliance "offensive and defensive."