After encircling the Soviet Red Army in late September 1941, Nazi forces captured Kyiv and promptly posted notices ordering Jews to gather near a place known as “Grandmother’s Ravine,” or “Babyn Yar” in local parlance. Days later, locals watched long columns of people shuffle past. On Sept. 29 and 30, SS-led forces gunned down nearly 34,000 Jews — not including children, who were often buried alive as Nazi policy forbade wasting bullets on them — and dumped them into the ravine. By the end of the war, some 100,000 dead, including thousands of Ukrainians and Roma, lay in the mass...