VERKHNE-BLAGOVESHCHENSK, Russia — The crime scene is a riverbank from which Russian Cossacks drove thousands of Chinese to their death by drowning in the Amur River 120 years ago. On a nearby hill stand a bronze memorial statue and a concrete Orthodox cross.

These memorials are not there to mourn the victims. Instead, they celebrate the Cossacks for their role in securing lands that were once Chinese but, since the middle of the 19th century, have been firmly part of the Russian Far East.

For two countries that revel in bitter memories of suffering at the hands of foreign intruders, the gruesome events on the Amur in 1900 present a ticklish problem. Russia and China now have close economic and political ties, and are bound together by shared wariness of the West and by highly selective memories of their own often fraught pasts.

“We need them and they need us,” said Olga Zalesskaia, a China expert and a dean at the Blagoveshchensk State Pedagogical University. “Now we are cooperating, and it makes no sense to stir up all the painful pages of the past.”