He admitted that NATO should respond to Russian provocations such as violation of NATO member states' airspace.
Duda believes that in such a way Russia can test the reaction of NATO.
"If these actions remain untrammelled, tomorrow we will have Russian planes over Prague, over Warsaw, and the day after tomorrow - perhaps over Berlin," the Polish president warned.
He states that in recent years people in Poland understood the importance of NATO membership.
"The geopolitical situation from 2008 to 2014, when Russia first attacked Georgia, and then Ukraine, has triggered the return of the old associations from the past - the imperial policy of Russia, the persecution of the West, the expansion of the sphere of influence, the occupation of more countries, and so on... And that is why we value NATO in Poland so much," said the Polish leader.