Historical links between Russia and Ukraine date back as far as the 9th century — a legacy Putin has invoked as a justification for his invasion of Ukraine. The Donbas region — which shares a border with Russia — has a long industrial heritage, with heavy mining and steel-producing capacity, as well as large coal reserves. In early 2014, after mass protests in Ukraine toppled a pro-Moscow president, Russia invaded and annexed Ukraine’s Crimean Peninsula — a move Europe and the United States saw as illegal. Moscow-backed separatists also took over the eastern regions of Donetsk and Luhansk on Russia’s border. There, the rebels seized government buildings and proclaimed new “people’s republics.” The crisis escalated, and pro-Russian separatists in Donetsk and Luhansk held a referendum to declare independence from Ukraine. Kyiv and the West have accused Russia of supporting the rebels with troops and weapons, but Russia says the fighters are volunteers. Clashes between the separatists and Kyiv-backed forces continued. In 2015, Russia and Ukraine agreed on the Minsk peace deal, a plan brokered by France and Germany to end the conflict between Kyiv and the Russian-backed separatists in the contested region. Under the agreement, Ukraine would give the two regions a special status and significant autonomy in return for regaining control of its border with Russia. But negotiations stalled. Putin said Ukraine has no intention of implementing the agreement’s terms. Ukraine said an agreement on Russian terms would give Moscow power to influence Ukraine’s foreign policy and undermine its sovereignty. Putin’s formal recognition of the Donetsk and Luhansk people’s republics Feb. 21, days before he launched his invasion, signaled an end to a seven-year-old peace deal. The failure of the Minsk agreement dampens hopes of a lasting peace deal to end the current fighting, analysts say. Ukrainian President Volodymyr Zelensky has accused Russia of killing civilians in places like the suburb of Bucha, where Ukraine has said mass graves and bodies on the street point to increasing evidence of massacres that will make reaching a peace agreement more difficult. Even before the Russian invasion, Moscow had issued 800,000 Russian passports in the separatist regions.