The Prince of Wales has thanked British troops for "defending our freedoms" in a secret visit to a military base in Poland near to the Ukraine border.
Prince William's visit to Rzeszow in south-eastern Poland was kept under wraps over security concerns until he left and arrived in the capital Warsaw.
He told British soldiers: "Thank you for all you are doing out here."
He said he wanted to thank them in person for "keeping everyone safe" and "keeping an eye on what's going on".
"So, just a big thank you for what you do on a day-to-day basis."
He added: "You're doing a really important job out here and defending our freedoms is really important, and everyone back home thoroughly supports you."
Rzeszow is just over an hour's drive from the Ukrainian border.
British, US and Polish troops are at the base to help secure Poland's airspace and to aid support to Ukraine.
Prince William's visit to Poland is at the request of the UK government, but the prince has been clear about his support for Ukraine from the start, tweeting his support to Ukraine just days after Russia's invasion.
His trip to Poland marks him renewing that support.On landing in Warsaw, the prince said: "It's fantastic to be back in Poland.
"Our nations have strong ties. Through our co-operation in support of the people of Ukraine and their freedom, which are also our freedoms and yours, these ties are further strengthened.
"I'm here because I want to personally thank the Polish and British troops working in close and crucial partnership.
"I also want to pay tribute to the inspiring humanity of the Polish people. You have opened your hearts as much as your homes."
As part of his two-day trip, on Thursday the prince will meet the Polish President Andrzej Duda at the Presidential Palace.
The heir to the throne is also due to visit a Ukrainian refugee centre in Warsaw and meet some of the 300 women and children housed there.
He will also lay a wreath at the Tomb of the Unknown Soldier, a monument dedicated to Polish soldiers who lost their lives in conflict.It is William's first trip to Poland since he visited in 2017 with his wife the Princess of Wales.
Last May, before he was king, King Charles III travelled to Romania to meet Ukrainian refugees - the first visit from a senior royal to the region since the start of the Russian invasion of Ukraine.
Poland is a strong ally of Ukraine one of the largest suppliers of military equipment.