Russian troops are reinforcing their position in Crimea in anticipation of attacks from Ukraine, a Russia-installed regional official admitted. “Fortification works aimed at guaranteeing Crimeans’ security are being conducted under my supervision,” Russia’s regional governor of the annexed peninsula, Sergei Aksyonov, said Friday. The prospect of a showdown over Crimea, which Russia annexed from Ukraine in 2014 in the clandestine operation that began the war, has loomed into view due to a series of Ukrainian successes in a counteroffensive conducted this fall. Russia’s retreat from the west bank of the Dnieper River not only freed the key city of Kherson...