He was a Wing Commander in the RAF, from Wiki :-
During World War II the German-born prince was part of the London-based Allied war planning councils and saw active service as a Wing Commander (RAF) flying both fighter and bomber planes into combat. He was a Dutch General and Supreme Commander of the Dutch Armed forces, involved in negotiating the terms of surrender of the German Army in the Netherlands.
For proven bravery, leadership and loyalty during his wartime efforts he was appointed a Commander of the Military William Order, the Netherlands' oldest and highest honour. After the War he was also made Honorary Air Marshal of the RAF by Queen Elizabeth II. In 1969, Bernhard was awarded the Grand Cross (Special Class) of the Order of Merit of the Federal Republic of Germany.