The headquarters of the 36th Ukrainian Naval Infantry Brigade based in the southern city of Mykolaiv is no more. It is now a pile of rubble, where on Saturday rescuers continued to search for bodies of missing marines. An early morning rocket attack a day earlier destroyed the base’s barracks where an unknown number of marines were sleeping. It killed more than 40 marines, according to a senior Ukrainian military official, who spoke on condition of anonymity to reveal sensitive military information. That number would make it one of the single deadliest attacks on Ukrainian forces since the start of...