Russia has managed to overcome sanctions and export controls imposed by the West to expand its missile production beyond prewar levels, according to U.S., European and Ukrainian officials, leaving Ukraine especially vulnerable to intensified attacks in the coming months... Overall, Kusti Salm, a senior Estonian defense ministry official, estimated that Russia’s current ammunition production is seven times greater than that of the West. Russia’s production costs are also far lower than the West’s, in part because Moscow is sacrificing safety and quality in its effort to build weapons more cheaply, Mr. Salm said. For instance, it costs a Western country...