While Elser was in the bierkeller he noted the stone pillar just behind the speaker’s dais; it supported a substantial balcony along one wall. His rough calculations suggested that a large bomb placed within the pillar would bring down the balcony and bury both the Führer and a number of his chief supporters. The question was how to conceal a device sufficiently powerful to do the job within a piece of solid stonework.It was only bad luck--that Hitler left his engagement a half-hour early--that the plot failed. Elser was soon arrested while attempting to escape from Germany. However, because the Germans could not believe that Elser acted alone, they kept him alive for years.
Here again Elser proved to have precisely the qualities needed for the job. Knowing that he had a year to prepare, he went to work methodically, obtaining a low-paying job in an arms factory and taking whatever opportunities presented themselves to smuggle 110 pounds of high explosives out of the plant. A temporary job in a quarry supplied him with dynamite and a quantity of high-capacity detonators. In the evenings, he returned to his apartment and worked on designs for a sophisticated time bomb.
In April 1939, Elser returned to Munich to carry out a detailed reconnaissance. He made sketches of the beer cellar and took more precise measurements. He also visited the Swiss frontier to work out an escape route, finding a stretch of the border that was not patrolled.
That August, as Hitler stoked up tension with Poland and Europe slipped toward war, Elser moved to Munich and began the final preparations for planting his device. The work involved huge risks and revealed an imaginative side to the bomber’s personality that few who knew him realized he possessed. Taking advantage of the Löwenbräu’s lax security, Elser became a regular customer. Each evening he would take his dinner there, order a beer and wait until closing time. Then he would slip upstairs, hide in a storeroom and emerge after 11:30 to get down to the crucial job of hollowing the pillar.
The work was astonishingly painstaking and slow. Working by flashlight, Elser first neatly cut a hole in some wood cladding; this job alone took him three nights. Next he attacked the pillar itself. The noise of a chisel striking stone echoed so loudly through the empty bierkeller that Elser restricted himself to single blows every few minutes, timing the descent of his hammer to coincide with the passing of a streetcar or the automatic flushing of the urinals. Every fleck of stone and piece of dust had to be swept up to leave no evidence of his work; then the panel he had cut out of the wood had to be seamlessly replaced before Elser made his escape through a side exit early the next morning. The carpenter returned to the bierkeller evening after evening, working on his plan for 35 nights in all. On one occasion he was nearly caught; a waiter found him inside the building as the place was opening and ran to tell the manager. Questioned, Elser insisted he was simply an early customer. He ordered a coffee, drank it in the garden and left unmolested.
It was typical of Elser that he labored to produce the most efficient bomb he could. By modifying a clock, he created a timer that would run for up to 144 hours before activating a lever; that would trigger a system of springs and weights that would launch a steel shuttle into a live rifle round embedded in explosive. Next, Elser added a second timer to act as a fail-safe, then enclosed the whole bomb in a beautifully built box designed to fit precisely into the cavity he had excavated. He minimized the risk of discovery by lining the cavity with cork, which muffled the noise from the bomb’s clock, and then placing a sheet of tinplate inside the wood panel to prevent any bierkeller worker putting up decorations from unknowingly driving a nail into his delicate mechanism. When he was finished, he returned to the bierkeller with the box he’d made and discovered that it was fractionally too big. He took it home, planed it down and went back again to make sure it fit.
Of course, given our knowledge of what Hitler was to do, we can view Mr. Elser in a heroic light. At the time he was arrested, he was nothing more than a "terrorist." If it wasn't for the Nazi officials taking a stance akin to "truthers"--that, notwithstanding all evidence to the contrary, Mr. Elser could not have accomplished what he did without the assistance of a government--Mr. Elser would have been tried and executed almost immediately.