Annexation
Annexation, in international law, is the forcible acquisition and assertion of legal title over one state's territory by another state, usually following military occupation of the territory. In current international law, it is generally held to be an illegal act. Annexation is a unilateral act where territory is seized and held by one state, as distinct from conquest, and differs from cession, in which territory is given or sold through treaty.
Annexation can be legitimized if generally recognized by other states and international bodies.
The illegality of annexation means that states carrying out such acts usually avoid using the word annexation in describing their actions; in each of the unresolved annexations by Israel, Morocco and Russia, the states have avoided characterizing their actions as such.