“The fire hurts where it hits,” Recep Tayyip Erdogan, then Turkey’s prime minister, said last year on the eve of an anniversary that he and his government would prefer to forget. Mr. Erdogan was using a popular saying to refer obliquely to the mass deportations and massacres of hundreds of thousands of Armenians and Assyrians in the Ottoman Empire in 1915.

In Turkey, the debate over what most scholars acknowledge as a genocide remains a festering concern for Mr. Erdogan, now Turkey’s president. His government’s policy is to deny it.

According to the official Turkish view, maintaining national security and a loyal population during World War I required harsh measures — including ethnic cleansing, forced assimilation and brutal reprisals against rebellious Armenians.

Mr. Erdogan has offered his condolences to the descendants of those massacred, thus shifting the state’s narrative from condemnation of treacherous rebels to sorrow for victims of war, both Christian and Muslim. “The incidents of the First World War are our shared pain,” he said last year, without distinguishing between battle deaths and those deliberately murdered by the Ottoman government and its agents.

Mr. Erdogan’s small but significant shift lags far behind the progressive forces in Turkey who speak openly about the mass killings that accompanied the end of the Ottoman Empire. Many of the millions of Kurdish citizens of Turkey, some of whom are descendants of perpetrators of anti-Armenian violence, have apologized for the genocide in which their forefathers participated. The Kurds have themselves been victims of Turkish state violence in the last century and now tell Armenians, “They had you for breakfast and will have us for dinner.” ...