Uranium

Uranium is a heavy metal, and Element 92 on the Periodic Table. It is used in the manufacture of atomic bombs.

Uranium in World War
When the Race invaded Earth, a number of nations were already looking into the manufacture of atomic bombs. Uranium atoms were known to be the least stable of the naturally occuring elements' atoms (though plutonium elements were larger and thus weaker]], and so were looked into by physicists. However, only the isotope U-235 is useful for atomic devices, and it is much rarer than U-238.  Physicists the world over were struggling to remove U-238 from uranium and be left with U-235--called Highly Enriched Uranium, or HEU.  They were having difficulty designing a practicable enrichment process.

Earth physicists were helped greatly when a sample of HEU was captured from a destroyed Lizard starship in a joint venture by the SS and the NKVD commanded by Otto Skorzeny. Germany and the Soviet Union divided the uranium equally, but since the raid occured within Soviet territory only the Russian uranium reached its intended destination; the German sample was once again divided in half when Heinrich Jager was captured by Mordechai Anielewicz while carrying it across Poland. He was allowed to carry half of his sample to Germany; the other half was sent to the United States on a British submarine where it was eventually carried to Denver by Leslie Groves.

The Soviets used their complete sample to build an atomic bomb, which they used as a defensive weapon to destroy one of the Race's armies in their territory. Neither the American nor the German samples were large enough for this, and so were used for research purposes. This is one reason why both the Germans and the Americans were able to enrich uranium on their own and construct their own bombs well ahead of the Soviets.

Physicists in several different countries also attempted to learn about the Race's successful enrichment techniques by interrogating POWs. In Japan, Teerts was coerced into sharing information with physicists. In the United States, Ullhass and Ristin were convinced to do so much more willingly.

Uranium in Southern Victory
Many countries, including the United States, the Confederate States, Britain, France, Germany, and Austria-Hungary are known to be attempting to construct atomic bombs. As of 1943, none were known to have enriched uranium successfully. Henry V. FitzBelmont explained several possible enrichment techniques he had thought of in his pitch to Jake Featherston, including gaseous diffusion using the highly toxic uranium hexafluoride. His inability to say with certainty whether any of these would work led Featherston to refuse to grant him the men and resources his proposed project would require.