UNITED STATES im ROPLY REFER TO. ATOMIC ENERGY COMMISSION WASHINGTON 25, D.C. MAT: NDG JAN2 i 1954 Major General P. W. Clarkson, USA Commander, Joint Task Force SEVEN Temporary "U" Euilding, Room 2005 12th and Constitution Avenue, N. W, Washington 25, D. C. Dear General Clarkson: Presidential appreval has been received for executing CASTLE with March 1, 195) as the starting date. Permission has also been eranted to detonate seven shots and to e.pend tissionable and fusionable materials in the amounts inaicated Ltelow. This letter should be construed as your authority to execute CASTLE as planned. Sincerely yours, K. D. Nichols General Manager Enclosure: Cys 1A & 24 Fissionable and Fusionable Haterial For CASTLE Devices 433 Lid