In March and April 2021, prior to the 2022 Russian invasion of Ukraine, the Russian Armed Forces began massing thousands of personnel and military equipment near Russia's border with Ukraine and in Crimea, representing the largest mobilisation since the illegal annexation of Crimea in 2014. This precipitated an international crisis due to concerns over a potential invasion. Satellite imagery showed movements of armour, missiles, and heavy weaponry towards the border. The troops were partially withdrawn by June 2021, though the infrastructure was left in place. A second build-up began in October 2021, this time with more soldiers and with deployments on new fronts; by December over 100,000 Russian troops were massed around Ukraine on three sides, including Belarus from the north and Crimea from the south. Despite the Russian military build-ups, Russian officials from November 2021 to 20 February 2022 repeatedly denied that Russia had plans to invade Ukraine.