This particular 'Fusion Pioneers Memorial lecture' was given 50 years after the first historical FEC conference in 1958. It was a unique occasion to perform a global reflection on thermonuclear fusion which is summarized in this paper. We first consider the case for fusion energy then move on to the scientific achievements during the past five decades. Finally, the lessons drawn from the past give a framework to consider the challenges ahead of us. The 1958 pioneers had the vision of the vital importance of international collaboration to succeed in this unique endeavour. Fifty years later, this vision has amply proven its worth. Looking at the way forward, this vision constitutes a strong basis to harness fusion energy in the decades to come.