Everett left Princeton in April 1956, returning in September to take his final examination for the Ph.D. degree  (the general examination had been graded "Good;" the final examination was graded "Very Good" ). Around this time he was among a select group of scientists invited to form a scientific core  of the Pentagon Weapons Systems Evaluation Group (WSEG) under the auspices of the Institute for Defense Analyses (IDA)-a civilian organization that could hire outstanding scientists and carry out defense work without the restricted salary levels of government employment . It is likely that Wheeler had a role in securing the invitation for Everett, which he (Everett) accepted .
In October 1956 Everett received orientation on "special weapons" (presumably nuclear weapons, to judge by the handsome certificate that he received with a mushroom cloud drawn in the center) by attending an Advanced Class at Sandia Laboratories in Albuquerque, New Mexico [40, 41]. There he acquired a familiarity with, and a life-long love for, computer modeling. When he directed the department of physical and mathematical sciences of WSEG, beginning in 1957, he gained a reputation as an advocate of ever more powerful computers, which took up ever more space. [13, 14]. IDA had offices in Alexandria , in the so-called "Paperclip" building [1a]. Until August 1957, Everett and his new wife lived in nearby Arlington, where the Pentagon  is located. For a little while in the spring of 1957 Everett had to tear himself away from problems of national security in order to complete his academic career.