Russia and Ukraine have had no formal diplomatic relations since 24 February 2022. The Russian Federation and Ukraine are currently in a state of war: the Russo-Ukrainian War began in 2014 following the Russian annexation of Crimea from Ukraine. In February 2022, Russia invaded Ukraine across a broad front. Relations between the two countries have been hostile since the 2014 Revolution of Dignity, which toppled Ukraine’s elected president Viktor Yanukovych and his supporters, because he refused to sign a political association and free trade agreement with the European Union that enjoyed majority support in Ukraine’s parliament. Ukraine’s post-revolutionary government wished to commit the country to a future within the EU and NATO, rather than continue to play the delicate diplomatic game of balancing its own economic and security interests with those of Russia, the EU, and NATO members. In 2004 the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, and Slovakia had joined the EU, followed by Bulgaria and Romania in 2007 (see Member state of the European Union). The Russian government feared that Ukraine’s membership of the EU and NATO would complete a western wall of allied countries by restricting Russia’s access to the Black Sea. With South Korea and Japan being allied to the US, the Russian government was concerned that Russia was being ring-fenced by potentially hostile powers. In the wake of the Revolution of Dignity, Russia backed separatist militias in the Donetsk People’s Republic and the Luhansk People’s Republic in a war in Ukraine’s economically important Donbas region, on its eastern border with Russia. This region has a Russian ethnic majority. By early 2022 the Russo-Ukrainian War had killed more than 13,000 people, and brought some Western sanctions on Russia. In 2019, amendments were made to the Constitution of Ukraine, which enshrined the irreversibility of the country’s strategic course towards EU and NATO membership. Throughout 2021 and 2022, Russian military buildup on the border of Ukraine has escalated tensions between the two countries and strained bilateral relations, with the United States sending a strong message that invasion would be met with dire consequences for Russia’s economy. On 24 February 2022, Russia invaded Ukraine, which prompted Ukraine to break diplomatic ties with its eastern neighbour.