For Poles, Sept. 17 is a day of mourning. On that date in 1939, 16 days after Adolf Hitler invaded Poland from the west, Josef Stalin’s Red Army invaded from the east, under the secret protocol to the Molotov-Ribbentrop Pact. Under communist rule, public commemoration of the date was censored and suppressed.

Seventy years later, on Sept. 17, 2009, the Obama administration announced it was abandoning the missile defense site former President George W. Bush had planned for Poland. The night before, then-President Barack Obama had tried to call Polish Prime Minister Donald Tusk. The call never took place. The Polish side proposed talking the next day instead.