Declassified photos show the US’s final preparations for the nuclear attacks on Hiroshima and Nagasaki

From there, both “Little Boy” and “Fat Man” were flown over Hiroshima and Nagasaki, respectively, dropped, and detonated. On August 15, Japan announced its intention to surrender, signing formal documents to that fact on September 2, ending World War II.

Once inside the plane, the bomb is secured and all connections and equipment are checked again.

Using the hydraulic lift, “Little Boy” is carefully raised and loaded into the belly of the Enola Gay.

The tarp is removed and the bomb is readied for loading.

Once “Little Boy” is ready, the Enola Gay, a Boeing B-29 Superfortress bomber, is reversed and positioned over the trench.

Workers check “Little Boy” one last time, keeping the tarp on for security reasons, following a lowering procedure similar to the one done for “Fat Man” three days later.

The bomb and its trailer are lowered down into the pit using a hydraulic lift.

Both pits for “Little Boy” and “Fat Man,” each roughly 8 feet by 12 feet, still exist today on the island and now serve as a memorial of sorts.

At the airfield, “Fat Man” is lined up over a pit specifically constructed for it, from which it is then loaded into the plane that eventually dropped it over Nagasaki.

The bomb is then escorted to the nearby North Field airbase on Tinian, shrouded by a tarp.

“Fat Man” is loaded onto a transport trailer and given a final once-over.

Here’s a closer look.

Soldiers and workers sign their names and other messages on the nose of “Fat Man.”

A technician applies sealant and putty to the crevices of “Fat Man,” a final preparation to make sure the environment inside the bomb would be stable enough to create a full impact once it detonated.

On the left, geophysicist and Manhattan Project participant Francis Birch marks the bomb unit that would become “Little Boy,” while Norman Ramsey, who would later win the Nobel Prize in physics, looks on.

Soldiers check the casings on the “Fat Man” atomic bomb. Multiple test bombs were created on Tinian Island. All were roughly identical to an operational bomb, even though they lacked the necessary equipment to detonate.