This is the 12715th most frequent Polish word.
niepodległe
"Niepodległe" means "independent" in English.
Here, 'niepodległe' is used as an adjective describing countries that are independent.
Niektóre kraje w Europie są niepodległe.
Some countries in Europe are independent.
In this sentence, 'niepodległa' is used as a predicate adjective referring to Poland achieving independence.
Po wielu latach walki, Polska stała się niepodległa.
After many years of struggle, Poland became independent.
The term 'niepodległego' acts here as an adjective modifying 'myślenia' (thinking), referring to thought that is free and independent.