Between February 20 and March 18, 2014, Russia militarily occupies the Crimean peninsula, Ukrainian territory. The operation begins with the appearance of so-called "little green men" — soldiers without insignia but with Russian equipment — who take control of government buildings and military bases.
On March 16, a referendum on independence is held, not recognized by the international community because it was conducted under military occupation. On March 18, Putin signs the annexation of Crimea to Russia.
The UN General Assembly adopts resolution 68/262 affirming Ukraine's territorial integrity and declaring the referendum invalid. 100 countries vote in favor, 11 against.
This action violates the Budapest Memorandum (1994), the UN Charter, and the Helsinki Final Act (1975) which guarantees the inviolability of borders in Europe.