As part of their training, they attended lectures by Edward Teller, Hans Bethe, Lise Meitner and Enrico Fermi. The electrical and mechanical groups at Sandia, although not the nuclear group, completed their training around the end of October 1946 and spent the next month devising the best methods of assembling a Fat Man, drawing up detailed checklists so later bomb assembly teams could be trained. They also drew up a proposed table of organization and equipment for an assembly team. It took two weeks for them to assemble their first bomb in December 1946. Most of 1947 was spent planning for a field exercise in which a bomb team would deploy to a base and assemble weapons under field conditions. A by portable building was acquired and outfitted as field workshops that could be loaded onto a C-54 or C-97 transport aircraft. In November 1947, the 38th Engineer Battalion carried out its first major field exercise, Operation Ajax. It drew bomb components, except for fissile cores, from the AEC, and deployed by air to Wendover Field, Utah. This was the home of the 509th Bombardment Group, which was the only unit operating Silverplate B-29 bombers, and therefore the only B-29 group capable of delivering nuclear weapons. To simulate operational conditions, they took a roundabout route via New England and Seattle. Over the following ten days, they assembled bombs and flew training missions with them, including a live drop at the Naval Ordnance Test Station at Inyokern, California. This was followed by other exercises. In one exercise in March 1948, the base personnel successfully fought off an "attack" by 250 paratroopers from Fort Hood, Texas. In another exercise in November 1948, the 471st Special Weapons Unit flew to Norfolk, Virginia, and practiced bomb assembly on board the Midway-class aircraft carriers. Nuclear testing In addition to assembly of weapons, the AFSWP supported nuclear weapons testing. For Operation Sandstone in 1948, Groves ordered Dorland to fill every possible job with his men. He did this so well that Strauss, now an AEC commissioner, became disturbed at the number of AFSWP personnel who were participating, and feared that the Soviet Union might launch a sneak attack on Enewetak to wipe out the nation's ability to assemble nuclear weapons. The successful testing in Operation Sandstone was a major leap forward. The new Mark 4 nuclear bomb the AEC began delivering in 1949 was a production