600 feet, the wind speed was 23 knots
from the southwest. The winds blew the cloud to the northeast (5).

2.1 PRESHOT ACTIVITIES

Construction of test site facilities on the Alamogordo Bombing Range
began in December 1944. The first contingent of personnel, 12
military policemen, arrived just before Christmas. The number of
personnel at the test site gradually increased until the peak level of
about 325 was reached the week before the detonation (2; 12).

On 7 May 1945 at 0437 hours, 200 LASL scientists and technicians
exploded 100 tons of conventional high explosives at the test site.
The explosives were stacked on top of a 20-foot tower and contained
tubes of radioactive solution to simulate, at a low level of activity,
the radioactive products expected from a nuclear explosion. The test
produced a bright sphere which spread out in an oval form. A column
of smoke and debris rose as high as 15,000 feet before drifting
eastward. The explosion left a shallow crater 1.5 meters deep and 9
meters wide. Monitoring in the area revealed a level of radioactivity
low enough to allow workers to spend several hours in the area (3;
12).

The planned firing date for the TRINITY device was 4 July 1945. On 14
June 1945, Dr. Oppenheimer changed the test date to no earlier than 13
July and no later than 23 July. On 30 June, the earliest firing date
was moved to 16 July, even though better weather was forecast for 18
and 19 July. Because the Allied conference in Potsdam, Germany, was
about to begin and the President needed the results of the test as
soon as possible, the TRINITY test organization adjusted its schedules
accordingly and set shot-time at 0400 hours on 16 July (3; 12; 14).

The final preparations for the detonation started at 2200 on 15 July.
To prevent unnecessary danger, all personnel not essential to the
firing activities were ordered to leave the test site. During the
night of 15 July, these people left for viewing positions on Compania
Hill,* 32 kilometers northwest of ground zero. They were joined by
several spectators from LASL (3; 12).

* "Compania" also appears as "Compana," "Campagne," or "Compagna" in
various sources.

Project personnel not required to check instruments within the ground
zero area stationed themselves in the three shelters or at other
assigned locations. The military police at Guard Posts 1, 2, and 4
blocked off all roads leading into the test site, and the men at Guard