On February 27, 2014, Russian forces moved into Crimea, a region belonging to Ukraine, marking a significant escalation in tensions between Russia and Western countries. Russian President Vladimir Putin authorized the military intervention and subsequent annexation of the peninsula, which had been part of Ukraine since 1954.

The operation followed political unrest in Ukraine, where protests led to the ousting of then-President Viktor Yanukovych. Russia cited the need to protect the rights of Russian-speaking residents in Crimea and expressed concerns about the new Ukrainian government's alignment with the West. Following the military deployment, authorities in Crimea held a controversial referendum on March 16, 2014, in which voters allegedly supported joining Russia. The annexation was formalized shortly thereafter.

This move ended a period of relatively cooperative relations between Russia and Western nations, triggering widespread condemnation. Western governments, including the United States and members of the European Union, rejected the legitimacy of the referendum, describing the annexation as a violation of international law and Ukrainian sovereignty. They imposed sanctions targeting Russian individuals, companies, and sectors in response.

Russia defended its actions as legal and justified, asserting historical and strategic claims over Crimea and emphasizing the expressed will of the local population. The annexation has led to ongoing conflict in eastern Ukraine and a significant deterioration of Russia’s diplomatic relationships with Western powers.

The situation remains a complex and contentious issue in international relations, with efforts toward resolution hindered by divergent positions on Crimea's status and broader regional security concerns.