The fall of Mariupol will free resources for Russia's offensive in eastern Ukraine's Donbas region, secure a land corridor to Crimea and boost Moscow's internal propaganda efforts. On May 22, the last Ukrainian forces held up in Mariupol's Azovstal steelworks on the Black Sea surrendered to Russian forces, after 86 days of resistance and on orders from Kyiv. Two days earlier, Russia's Ministry of Defense claimed that since May 16, a total of 2,439 Ukrainian soldiers had surrendered at the plant. Russian Defense Minister Sergei Shoigu also reported to President Vladimir Putin on the complete liberation of the plant and the city of Mariupol. While Kyiv hopes the Ukrainian troops will be part of a prisoner exchange, the terms of the defenders' surrender are unclear. Even if an understanding was struck, however, there is no guarantee Russia will honor that commitment as Moscow will likely attempt to use the surrendered...