Donald Trump congratulated Poland as they marked the 80th anniversary of Nazi invasion

US President Donald Trump congratulated Poland on his return to the White House on Sunday. Poland was commemorating the Nazi invasion 80 years ago. Photo / AP

In one of his helicopter-tinged news conferences that are becoming a trademark of his administration, US President Donald Trump on Sunday was asked if he had a message for Poland.

Trump was scheduled to attend a ceremony in Poland, but sent Vice President Mike Pence instead so Trump could monitor the situation with Hurricane Dorian.

"I just want to congratulate Poland. It's a great country, with great people," President Trump responded.

So what was he congratulating?

Unclear, but the ceremony he was supposed to attend commemorated the Nazi invasion of Poland 80 years ago.

This is what happened on September 1, 1939: At dawn, the German Luftwaffe started bombing a Polish town called Wielun. By the time they were done, they had flattened nearly three-quarters of the city, including a hospital and a Gothic church. Up to 1200 civilians were killed that day, according to the Polish government. There were no Polish troops stationed at Wielun and destroying it served no strategic purpose - Nazi Germany attacked it simply to sow terror, according to the BBC.

US Vice President Mike Pence, Polish President Andrzej Duda, centre and German President Frank-Walter Steinmeier during a ceremony marking the 80th anniversary of the start of World War II. Photo / AP

In fact, Poland had mobilised late and was completely unprepared for the invasion, according to the US Holocaust Memorial Museum. Poland had had a nonaggression agreement with Germany since 1934, but the Nazis invented a reason to violate it, staging a fake Polish attack on German radio.

A few hours after the attack began, Nazi leader Adolf Hitler went before the Reichstag and declared war against Poland.

Two days later, France and England declared war on Germany, marking the start of World War II.

Over the following weeks, more than 2000 German tanks and 1000 German warplanes pulverised the western part of Poland. After surrounding Warsaw and bombing it at will, the city surrendered to the Nazis on September 27, 1939.

Mike Pence rings the Bell of Memory and Warning during a memorial ceremony marking the 80th anniversary of the start of World War II in Warsaw, Poland. Photo / AP

Meanwhile, the Soviet Union, which had secretly agreed not to defend Poland against the Nazis, invaded the eastern part of Poland, which fell on October 6, 1939.

Over the next six years, Nazis killed at least 5 million Polish citizens, nearly one in every five citizens, according to estimates. More than half of them were Polish Jews.

The Nazis' most notorious death camp, Auschwitz, where more than 1 million people were killed, is located in southern Poland.

The Soviet Union liberated Poland in 1945, but it continued to struggle. A "compliant" government was promptly installed, according to the BBC, and Poland remained behind the Iron Curtain until 1989.

If "congratulations" for this from Trump seems out of place, then it may be just as well that Pence went in his place. As The Washington Post's Aaron Blake wrote, Pence struck a solemn chord on Sunday, saying, "It is difficult for any of us who are not Poles to fathom the horrors that began here 80 years ago, on this day."