Manhattan Project

            Despite the fact that the Manhattan Project was officially begun in August, the project actually stared in September when then Colonial Leslie Groves was called in from overseas to oversee it1.  Leslie was the son of an Army Chaplin who grew up traveling between different US military bases.  He graduated fourth in his class from West Point, whereupon he joined the Army Corps of Engineers.  After he graduated he held many posts, including overseeing the construction of the Pentagon.  He then went overseas seeking combat, but was soon transferred to the Manhattan Project and promoted to Brigadier General2.

It took him only two days to resolve the problems that had been slowing the program’s development prior to his arrival.  He quickly purchased 1250 tons of uranium and 52,000 acres of land which would later become Oak Ridge. By September 26th he had primary access to government and military resourses3.

Groves had a very militant style of leadership which put him at odds with many of the scientists working under him, especially with Szilard.  But after all was said and done and once the war was over, they all realized how necessary his leadership and strict organization had been4.

That fall, Groves decided that it would be better to have corporations build the production plants for the uranium and he ordered that construction of these plants begin immediately.  Even though exact designs and plans had not been made, Groves intelligently realized that no matter what the plans ended up looking like, the groundwork would be the same and it should start sooner than later5.

On October 15th of 1942 Groves asked Dr. Oppenheimer to head the central laboratory at Los Alamos which he was planning on having built6.  J. Robert Oppenheimer was born into a wealthy New York family.  Although he was sickly as a child, he proved himself outstandingly in academia, graduating summa cum laude from Harvard having studied poetry, Greek, chemistry, and physics.  He then took his studies abroad, getting his PhD and publishing 16 papers before coming back to the United States, where he became close friends with many people who joined the communist party, and married a German immigrant who was far along the path to communism herself.  The United States government therefore had reservations about placing him at the head of the program to build a bomb, but they did, and he performed very well in that position7.

A picture of Dr. Oppenheimer and General Groves This picture was found on the United States Government Department of Energy Office of History & Heritage's "The Manhattan Project" Site.

Oppenheimer had displayed wonderful leadership abilities during the S-1 project, and Groves, noticing this, worked together with him on their nuclear project.  Each recognized the other’s importance to the project from the very beginning, so Oppenheimer did not have the same problems with Groves that many other scientists had8.

On December 1st Enrico Fermi and his group of scientists were done with their project.  It contained 36.6 metric tons of uranium oxide, 5.6 metric tons of pure uranium metal, and a staggering 350 metric tons of graphite.  It was successfully tested the next day and was eventually operated a 200 watts9.

In January of 1943 Groves got an industrial complex in Washington to build plants for the reactors and separators of plutonium.  In March Los Alamos opened its doors and began to work10.  One author describes her first trip by Los Alamos thusly: “It’s easy to feel watched in Los Alamos.  During my first trip to the town several years ago, I stopped at the side of the road to take a picture of what I though was just the Santa Fe National Forest.  A small pickup truck did a quick U-turn and parked next to me until I left.  When this happened again on another public highway in the area, I began to wonder whose woods these really were.  Later I learned that the technical areas of Los Alamos National Laboratory extend far beyond the obvious cluster of grey and tan buildings at its center.  They are spread over forty-three square miles of woods and canyons and are hemmed in by national forests and parklands.  It turns out I was nowhere near the heavily guarded areas of the lab, where picture taking would be considered a threat to national security. But I was quietly watched nonetheless”11.  Over the remainder of the year the buildings were under construction.  Other than that the only two events of true import were the creation of the X-10 graphite reactor, which provided enough plutonium for research purposes and began working on November 4th and Project Alberta’s birth.  Project Alberta was meant to make the real world delivery possible12.

A picture of one of the more luxurious places to stay in Los Alamos. It was reserved for special guests and high-ranking personnel.  This picture was found on the United States Government Department of Energy Office of History & Heritage's "The Manhattan Project" Site.

1944 brought with it increased productivity in weapon development, production of material to undergo fission, and combat delivery groundwork.  However there were a few problems.  First was a problem with one of the plants built at Oak Ridge.  This was solved by information leaked to Oppenheimer from Abelson, who was constructing a different kind of plant.  The second major problem was when Emilio Segre discovered that plutonium underwent fission far too quickly for the method of delivery upon which all of the Manhattan Project’s research had focused.  Once verified, this discovery meant that Oppenheimer needed to give his full effort and attention to putting together implosion technology as well as to creating a fundamentally new technology, explosive wave shaping13.

And so progress on the Manhattan Project moved slowly, while Project Alberta moved forward very quickly, having already modified several bombers and begun training of the 509th Composite Group to deliver the bombs in combat.  By the end of the year however, things were doing much better.  Enriched uranium production reached 90g/day, the first successful explosive lens was tested, and large scale plutonium production had begun14.

A picture of a meeting of Los Alamos Scientists  This picture was found on the United States Government Department of Energy Office of History & Heritage's "The Manhattan Project" Site.

At the beginning of 1945 uranium bombs looked to be a certain success within months, and the prospects of a plutonium bomb were looking a lot better than they had previously15.

In January it was estimated that there would be enough uranium to make a bomb on July 1st.  In February larger amounts of Plutonium were being shipped to Los Alamos from Hanford, and Tinian Island was chosen as a base of operations.  In April preparation began to set up Tinian Island, Roosevelt died, and Truman learned about the existence of the atomic bomb, and several potential targets were chosen and eliminated.  In May, the 100-ton test was completed successfully, Germany surrendered, the list of targets shrank to, Hiroshima and Niigata, and the bomb Little Boy was ready except for its uranium core which was estimated to be complete on August 1st.  In June, the 509th begin arriving on Tinian and the implosion core design is confirmed as satisfactory.  In July, lens castings were selected, the assembly of Gadget, the first bomb, began, Little Boy was shipped off to Tinian, the only test for a plutonium lens system was completed it was first thought a failure, but was proven to be a success when calculations were corrected, and Gadget was detonated on July 16th at 5:29:45 AM, it is the first atomic explosion in history, and the yield was between 20 and 22 kilotons16.

A picture of the explosion made by the testing of the first nuclear weapon.  This picture was found on the United States Government Department of Energy Office of History & Heritage's "The Manhattan Project" Site.


Sources for this Page



1.   The Nuclear Weapon Archive.

2.   Diehl, Sarah J., and James Clay Moltz. Nuclear Weapons and Nonproliferation. 2nd ed. Santa Barbara:                     ABC-CLIO Inc., 2008.

3.   The Nuclear Weapon Archive.

4.   The Nuclear Weapon Archive.

5.   The Nuclear Weapon Archive.

6.   The Nuclear Weapon Archive.

7.   Diehl, Sarah J., and James Clay Moltz. Nuclear Weapons and Nonproliferation. 2nd ed. Santa Barbara:                     ABC-CLIO Inc., 2008.

8.   The Nuclear Weapon Archive.

9.   The Nuclear Weapon Archive.

10. The Nuclear Weapon Archive.

11. Shroyer, Jo Ann. Secret Mesa: Inside Los Alamos National Laboratory. New York: John Wiley & Sons                            Inc., 1998.

12. The Nuclear Weapon Archive.

13. The Nuclear Weapon Archive.

14. The Nuclear Weapon Archive.

15. The Nuclear Weapon Archive.

16. The Nuclear Weapon Archive.