The often circumspect Koeman said it was a statement performance from his players who needed to silence the critics who had questioned their effort and commitment.
"We had to suffer tonight but there is not an easy one in a tournament like this. The players put everything tonight, it was really an emotional match and they showed a big heart," Koeman told a press conference.
"Sometimes we get critiques about that, that we don't have that compared to other nations. And the players showed tonight a big heart after going one nil down and made a good second half."
It was the first time the Netherlands reached a Euro semi-final in 20 years and they have fond memories of the last time the European Championship was hosted in Germany – their victory in the 1988 final remains their only major tournament success.
Koeman, a defender in the 1988-winning side packed with individual talent such as Ruud Gullit and Marco van Basten, said the strength of his team was their depth.
"I think for the whole nation it's something special," Koeman said.
"We are a small nation and we are part of the semi-final with England, France and Spain... We are really proud to get the opportunity to play for a spot in the final on Wednesday.
"England have good players, but we have too. We play in Dortmund, in one of the most beautiful stadiums, closer to the Netherlands, maybe that also makes a difference.
