Russian attacks throughout eastern Ukraine killed at least 27 people on Tuesday, including 12 in one of the worst strikes so far this year, hours before a midnight deadline ushering in an open-ended ceasefire proposed by Kyiv. Russia announced a ceasefire for May 8 to 9 to coincide with commemorations of the Soviet Union’s victory over Nazi Germany in World War II and a military parade in Moscow’s Red Square. Ukraine, in response, announced a proposal for an open-ended ceasefire starting at...