In Pash’s view, Oppenheimer’s role in hiring Weinberg helped seal the case against the man Groves had chosen to lead Los Alamos.119 But the identification of Joe was overshadowed by the news—received that same day, via a wiretap on Oppie’s telephone—that the Los Alamos director was planning a surprise visit to Berkeley. Pash excitedly cabled Lansdale that he was preparing a reception: “Oppenheimer will be covered on arrival. Details by airmail. This office setting out all leads.”120
* * *
Oppenheimer arrived in Berkeley on Saturday, June 12, ostensibly to recruit a personal assistant.121 But his real purpose was to visit Jean Tatlock, whom he had avoided seeing before he left Berkeley.122 Tatlock was being treated for depression at Mt. Zion Hospital in San Francisco and had recently sent word to Los Alamos via Oppie’s former landlady that she wanted to see him.
For his assistant, Oppie chose David Hawkins, a young philosophy professor from Berkeley whom his brother, Frank, had known at Stanford. Army CIC agents followed Oppenheimer to Hawkins’s apartment in the Sunset district of San Francisco and later put a tap on Hawkins’s telephone.123
On Sunday evening, Oppenheimer had dinner with Lawrence, who was, as usual, cheerily optimistic about the progress of his Calutrons. Army agents in an adjoining booth at the restaurant overheard Ernest report that the lab was within sight of another milestone: 1 gram of U-235 per day.
On Monday morning, Oppie took the Key System train across the bridge to Jean Tatlock’s apartment on Montgomery Street, with Pash’s agents in tow. The couple had dinner at the Xochinilco Café on Broadway before returning to her apartment, where Oppenheimer spent the night. Army agents waited in a car parked on the street below.
Tuesday morning, Oppenheimer took the train back to Berkeley. He and Tatlock met again that evening for dinner, and afterward she drove him to the airport. Since Oppie had originally planned to be back in Los Alamos by Monday night, his tardiness required him to break Groves’s rule that grounded laboratory directors.
Oppenheimer’s rendezvous with Tatlock and his hiring of Hawkins—another suspected Communist—added further fuel to G-2’s suspicions.124 Pash warned Washington that the Los Alamos director was deliberately luring left-wing associates to the lab. Pash even hinted to Lansdale that Oppie might have agreed to work on the bomb just so he could give it to the Russians.125 The army asked the FBI to investigate Hawkins and to plant a bug in Tatlock’s apartment.126 Pieper—protesting that Pash was asking the bureau to “run errands”—initially refused both requests but later relented.127
Aware that Groves seemed committed to Oppenheimer, Pash broached with Lansdale the possibility of gradually easing Oppie out of his job at Los Alamos and replacing him with another scientist.128 The FBI’s Whitson also raised the question of firing Oppenheimer. Groves, however, would have none of it, as Pash and the bureau learned from the project’s head of security: “Lansdale stated that General Groves claims flatly that Oppenheimer is irreplaceable and that if anything happened to Oppenheimer, the project would be set back at least six months.”129 Moreover, Groves had argued, such a delay could be catastrophic—since recent intelligence showed that the Germans were laying new high-tension wires, leading the army to conclude that the Nazis might be building their own Calutrons.
A few weeks later, on July 20, 1943, Groves put a quick and decisive end to the long agonizing over Oppenheimer by summarily ordering the district engineer to issue a security clearance for Oppie “without delay, irrespective of the information which you have concerning Mr. Oppenheimer. He is absolutely essential to the project.”130
6
A QUESTION OF DIVIDED LOYALTIES
LANSDALE DECIDED UPON a quick visit to the desert mesa later that summer, to take his own measure of Oppenheimer. Without alluding to the FBI’s wiretaps, Groves’s security man told Oppie that Lomanitz had remained active in FAECT and other radical causes. Oppenheimer expressed anger at the graduate student, saying that he wanted no Communists working on the project, for “one always had a question of divided loyalties.”1 Lansdale was just about to ask Oppenheimer for the names of party members at Los Alamos—he had told Whitson that he intended to fire them all—when the conversation was interrupted. The question remained unasked.
Lansdale came away from his visit convinced that Oppenheimer’s ego and Kitty’s vicarious ambition for her husband were the two best reasons for believing that neither would endanger the success of the project by allowing its secrets to be passed to the Russians. When the head of MED security shared this view with Groves, the general agreed.2
At Los Alamos, de Silva had already alienated the scientists by imposing new restrictions on travel to Santa Fe and by confiscating their cameras—measures for which Groves, as usual, got the blame.3
* * *
The bad news had come to Berkeley early in 1943, when Oppie had informed Lawrence that calculations indicated the fissionable material for the bomb had to be more than 90 percent pure U-235. Using uranium of any lower enrichment would mean a weapon too big and too heavy for a bomber to carry.4 Accordingly, the metal produced by the Alpha Calutrons would have to undergo a second, more careful separation. Lawrence and the boys had already designed a new machine for the purpose.5
Groves, looking ahead, also wanted to use the so-called Beta Calutrons to further enrich uranium that had been separated by other methods like gaseous diffusion. Work was begun on two Beta racetracks alongside the five Alpha Calutron racetracks already under construction on the 825-acre plot of land southeast of Oak Ridge. Lawrence’s cyclotroneers had meanwhile given Y-12 their own, more affectionate appellation: “Dogpatch.”6
By any scale, the operation there was mammoth. Plans called for installing a pair of 500-tank Calutron racetracks end-to-end in twin two-story buildings, each measuring more than four football fields long. The racetracks were on the second story; pumps and plumbing for the vacuum system occupied the first floor.7 A third building would hold the fifth and
