UNITED STATES ATOMIC ENERGY COMMISSION IN ROPLY REFER TO: MAT: NDG WASHINGTON 25, D.c. JAN2 3 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 approval has been received for executing CASTLE with March 1, 195 as the starting date. Permission as also sionable and fusionable materials in the amounts inaicated Lelbw. been eranted to detonate seven shots and to expend fi This letter should be construed as your authority to Pxecute CASTLE as planned. Sincerely yours, K. D. Nichols General Manager Enclosure: Cys 1A & 2A Fissionable and Fusionable Haterial For CASTLE Devices 433 j tS