Niels Bohr and Margrethe Nørlund were engaged in August 1910, less than a year before Bohr completed his doctoral work. Bohr then went to Cambridge and Manchester to continue his studies with J.J. Thomson and Ernest Rutherford, respectively. Niels and Margrethe married on Niels's return to Copenhagen in August 1912. Bohr's stay in England was an immensely creative period in his life, as confirmed by the intensive correspondence with his fiancée, who stayed behind in Denmark. The letters shed new light on this crucial period of Bohr's career and document the importance not only of Margrethe, but also of his family in Denmark, for Bohr's early development as a scientist and human being.