evidence: The Ukrainian ships had attempted to pass from Ukraine’s port at Odessa to its port at Mariupol, on the Sea of Azov. Doing so requires transiting the very narrow and shallow Kerch Strait, over which Russia has now built a road and rail bridge connecting Russia with Russian-occupied Crimea. The Ukrainian vessels refused to recognize Russia’s assertion of unilateral control over the strait or to comply with the instructions of the Russian Coast Guard to wait outside the strait. The ships proceeded anyway and were first blocked, then attacked by the Russian Coast Guard. By firing on the Ukrainian naval ships in international waters, by treating Ukraine’s sailors as civilians rather than members of a sovereign state’s armed forces, and by basing these actions on its claimed annexation of Crimea and its territorial waters, Russia violated international law, the laws of armed conflict, and a 2003 bilateral agreement in which Russia and Ukraine agreed to share sovereignty and control over the Sea of Azov and the Kerch Strait. Russia argues that it now has sole sovereignty over the strait; most of the world disagrees. [...] On the economic side, the European Union and United States should introduce sanctions tied specifically to Russia’s unilateral claim to control the Kerch Straits and access to the Sea of Azov. The United States should also redouble efforts to persuade Germany to defer the Nord Stream 2 gas pipeline project, at least as long as Russia’s aggression against Ukraine continues—or better yet, to cancel it altogether.