Taylor Swift has issued a warning to fans not to panic when they hear loud sirens in honor of a key World War II anniversary on the afternoon of her concert in Warsaw on Thursday.

Swift is set to perform in the Polish capital for thousands of ticketholders, many of whom will likely have traveled in from afar, while it commemorates the 80th anniversary of the start of the 1944 Warsaw Uprising, a 63-day revolt by Polish insurgents after five years of Nazi German occupation.

The remembrance involves the entire city stopping to listen to alarm sirens ringing out every year on August 1, at about 5 p.m., the exact time when the revolt was launched.

Swift’s Eras Tour account posted on X, “To the people who are coming to the concert on August 1st don’t panic if you heard sirens alarm about 5p.m. It will be 80th anniversary & planes!”

A similar warning was also broadcasted by a Polish news site, Onet, which wrote an article titled, “Important message for all Swifties who are going to the concert,” explaining the significance of the day. The article added, “We ask you to remain calm and not to panic. In this way every year residents pay tribute to the heroes of 1944. Those who will be at that moment already outside the stadium, please remain quiet and get up.”

On August 1, 1944, city residents rose up against the German forces that had occupied their nation for five years. The Soviets were approaching in their march westward against the German forces, and the Polish people held out hope for help. The Germans, with their professional army and superior weaponry, killed 200,000 Polish fighters and civilians.