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 the complete conquest of another country, and differs from cession, in which territory is given or sold through treaty.
Tourists in Crimea with the Russian flag flying after annexation by Russia (14 June 2015)
Civilians and coalition military forces wave Kuwaiti and Saudi Arabian flags as they celebrate the reversal of the annexation of Kuwait by Iraq (28 February 1991)
Communist Party of Vietnam billboard marking the 30th anniversary of the reunification of the country in 1975
In February and March 2014, Russia invaded the Crimean Peninsula, part of Ukraine, and then annexed it. This took place in the relative power vacuum immediately following the Revolution of Dignity. It marked the beginning of the Russo-Ukrainian War.
Russian President Vladimir Putin signs the treaty of accession (annexation) with Crimean leaders in Moscow, 18 March 2014.
Euromaidan in Kyiv, 11 December 2013
"Crimean self-defence forces", 2 March 2014
A pro-Ukrainian demonstration in Simferopol (Ukrainian flag on the left, Crimean Tatar flag on the right) during the Russian military intervention in Crimea, 9 March 2014