Germany and Poland have marked the 50th anniversary of German Chancellor Willy Brandt's gesture of apology for Nazi crimes.
Brandt famously fell to his knees after adjusting the wreath ribbons at the Warsaw Ghetto memorial on December 7, 1970.
Germany's then-chancellor, who had been in exile for much of the Nazi era, remained silently on his knees for several moments, surrounded by dignitaries and photographers.
The gesture, known as "Kniefall von Warschau", became a worldwide symbol of Germany's reconciliation with Poland and the foundation of modern relations.
Chancellor Brandt was also instrumental in the signing of a treaty which recognised the international border at the Oder and Neisse rivers. The treaty gave up Germany's claim to the territories it ceded to Poland after World War II.
However, at the time, several conservative commentators criticised Brandt's gesture as humiliating for all German citizens.
The former Chancellor, who died in October 1992, has always asserted that his fall to his knees was spontaneous.
"I hadn't planned anything, but left Wilanow Castle, where I was staying, with the feeling that I had to express the speciality of the memorial at the ghetto monument," he wrote in his memoirs.
"At the abyss of German history and under the burden of the murdered, I did what people do when the language fails."
On Monday, senior representatives from both Germany and Poland commemorated the anniversary by laying wreaths at the monument in the Polish capital.
"For us Poles, the kneeling of Chancellor Willy Brandt had great significance," said a statement by the Chancellery of President Andrzej Duda.
"There are actions that turn out to be icons that can express more than words".
The Head of the Polish Chancellery, Krzysztof Szczerski, was joined by State Secretary Stephan Steinlein, and the German Ambassador in Warsaw, Arndt Freytag von Loringhoven.
"The partnership between Germany and Poland is an important prerequisite for a successful future," said German Federal President Frank-Walter Steinmeier in a video message on the anniversary.
"But we will not forget the past either. Not the suffering of the people in Poland, not the historical courage for reconciliation and not even a kneel that reminds us of all that."
"Today we live in a Europe for which Willy Brandt laid the foundations," added German Foreign Minister Heiko Maas on Twitter.
"Further reconciliation with our eastern neighbours, especially Poland, remains our great task."