In June 1946, within a year of the termination of fighting in WWII, he arranged for an international meeting of crystallographers in London which was attended by some 120 scientists from most of the allied countries. In that London meeting Ewald was elected Chairman of the Provisional International Crystallographic Committee, which put into action the decision to form the International Union of Crystallography.
In June 1946, shortly after the end of WWII, he organized a global gathering of crystallographers in London that was attended by around 120 scientists from most of the allied nations. At this London conference, Ewald was elected chairman of the Provisional International Crystallographic Committee, which implemented the decision to establish the International Union of Crystallography.