Russian President Vladimir Putin is claiming control over Ukraine’s seaside city of Mariupol even as its defenders are holding out inside a massive steel mill near the water. His statement reflects the importance of the Sea of Azov port and appeared to be a Kremlin attempt to declare victory without storming the Azovstal plant, which represents the last Ukrainian resistance there. Mariupol is part of eastern Ukraine’s industrial region known as the Donbas and a key objective since the Feb. 24 invasion began. Its capture would allow Russia to establish a land corridor from its border to the Crimean Peninsula, which was annexed from Ukraine in 2014. It also would deprive Ukraine of a major port and industrial assets.