Henry Thomas Tizard's greatness shone most brilliantly in war and in the preparation for war. He had a genius, to a degree never surpassed, for applying scientific ideas and technological advances to military purposes. For this he is world famous. Professor P. M. S. Blackett has, however, given a vivid and penetrating account of Tizard's achievement in this field in his lecture to the Institute for Strategic Studies, to which I have little to add.