On rare occasions, events of transcendent importance are described in a paper of corresponding significance. The following presentation, prepared by two Past-Presidents of The Institute of Radio Engineers (IRE) who were official United States scientific observers of Operation Crossroads, is a contribution of this unusual sort. It is most earnestly commended to the thoughtful attention of the readers of the PROCEEDINGS OF THE IRE and for such comments and actions by them as may further the aims which it outlines. In view of the special circumstances surrounding this paper, The Institute of Radio Engineers grants permission to all publications in any language to reprint this paper in part or in its entirety, accompanied only by a simple acknowledgement of its source.