Devastation caused by an atomic bomb is seen in Nagasaki, Japan March 17, 1948. Department of Energy/Lawrence Berkeley National Laboratory/Handout via REUTERS.

U.S. troops arrive the month after an atomic bomb was dropped on Nagasaki, Japan in September 1945. Naval History and Heritage Command/Handout via REUTERS.

A bridge 4,400 feet (1.34 km) east of the detonation center of the atomic bomb blast is seen in Hiroshima, Japan in an undated photograph. U.S. Army/Library of Congress/Handout via REUTERS.

Japanese representatives, Foreign Minister Mamoru Shigemitsu and General Yoshijiro Umezu, Chief of the Army General Staff attend the surrender ceremonies on board the U.S. Navy battleship USS Missouri in Tokyo Bay, Japan September 2, 1945. U.S. Army Signal Corps/U.S. National Archives.

A Japanese soldier walks through the atomic-bomb leveled city of Hiroshima, Japan in September 1945. Lieutenant Wayne Miller, USNR/Naval History and Heritage Command/Handout via REUTERS.

Aerial pictures of Hiroshima taken in April 1945 before the atomic bomb was dropped and, in August 1945 after the bombing, show the extent of the devastation on the city. August 6, 2005 marks the 60th anniversary of the bombing, which instantly killed about 78,000 people. These photos were part of the records of the U.S. Strategic Bombing Survey.

Devastation caused by an atomic bomb is seen in Nagasaki, Japan March 17, 1948. Department of Energy/Lawrence Berkeley National Laboratory/Handout via REUTERS.

-FILE PHOTO MARCH 1946 - This general view of the city of Hiroshima showing damage wrought by the atomic bomb was taken March 1946, six months after the bomb was dropped August 6, 1945. The 50th anniversary of the bombing of Hiroshima and the end of World War II is August 1995

General of the Army Douglas MacArthur signs the Instrument of Surrender, as Supreme Allied Commander, on board the U.S. Navy battleship USS Missouri in Tokyo Bay, Japan September 2, 1945. Behind him are Lieutenant General Jonathan M. Wainwright, U.S. Army, and Lieutenant General Sir Arthur E. Percival, British Army, both of whom had just been released from Japanese prison camps. Officers in the front row, from Percival on, are (L-R): Vice Admiral John S. McCain; Vice Admiral John H. Towers; Admiral Richmond K. Turner; Admiral William F. Halsey; Rear Admiral Robert B. Carney; Rear Admiral Forrest Sherman; General Walter C. Krueger; General Robert L. Eichelberger; General Carl A. Spaatz and General George C. Kenney. U.S. Army Signal Corps/U.S. National Archives.

The Boeing B-29 Superfortress "Enola Gay" lands at the Tinian airbase in the Mariana Islands after the atomic bombing mission on Hiroshima, Japan in this U.S. Air Force handout photo dated August 6, 1945.

Devastation is seen in the vicinity of 'ground zero' after the atomic bombing of Hiroshima, Japan in an undated photograph. Department of Defense/Department of the Air Force/Handout via REUTERS.

Japan's Foreign Minister Mamoru Shigemitsu signs the Instrument of Surrender on behalf of the Japanese Government, on board the U.S. Navy battleship USS Missouri in Tokyo Bay, Japan September 2, 1945. Lieutentant General Richard K. Sutherland, U.S. Army, watches from the opposite side of the table. Foreign Ministry representative Toshikazu Kase is assisting Mr. Shigemitsu. U.S. Army Signal Corps/U.S. National Archives.

An aerial view taken by a reconaissance camera shows the city before the atomic bomb strike over Hiroshima, Japan in 1945. U.S. Army Air Forces/Library of Congress/Handout via REUTERS.

People walk past the devastation caused by an atomic bomb in Nagasaki, Japan March 17, 1948. Department of Energy/Lawrence Berkeley National Laboratory/Handout via REUTERS.

A man being treated for wounds caused by an atomic bomb is seen in Nagasaki, Japan in an undated photograph. War Department/U.S. National Archives/Handout via REUTERS.

Sailors watch as Japan's Foreign Ministry representatives Katsuo Okazaki and Toshikazu Kase, and Lieutenant General Richard K. Sutherland, U.S. Army, correct an error on the Japanese copy of the Instrument of Surrender, at the conclusion of the surrender ceremonies on board the U.S. Navy battship USS Missouri in Tokyo Bay, Japan September 2, 1945. U.S. Army Signal Corps/U.S. National Archives.

The ground crew of the B-29 "Enola Gay" which atom-bombed Hiroshima, Japan on August 6, 1945 poses for a photo with the aircraft at their base in Tinian, Mariana Islands in this undated U.S. Air Force handout image. Colonel Paul Tibbets, the pilot, stands in the center.

An atomic bomb of the "Fat Man" type, the kind which detonated over Nagasaki, Japan, is seen in an undated photograph. War Department/Office of the Chief of Engineers/Manhattan Engineer District/Handout via REUTERS.

Devastation caused by an atomic bomb is seen in Hiroshima, Japan in an undated photograph. War Department/U.S. National Archives/Handout via REUTERS.

Smoke rises more than 60,000 feet into the air over Nagasaki from an atomic bomb, the second ever used in warfare, dropped from a B-29 Superfortress bomber in this U.S. Air Force handout photo dated August 9, 1945.

People walk along a road cleared of the debris caused by an atomic bomb in Hiroshima, Japan in an undated photograph. War Department/U.S. National Archives/Handout via REUTERS.

A tricycle and helmet are displayed at Hiroshima Peace Memorial Museum in Hiroshima, Japan, June 1, 2016. Picture taken June 1, 2016. U.S. Air Force/Airman 1st Class Elizabeth Baker/Handout via REUTERS.

Smoke billows 20,000 feet (6100 metres) after an atomic bomb codenamed "Little Boy" exploded after being dropped by a U.S. Army Air Force B-29 bomber named "Enola Gay" over Hiroshima, Japan August 6, 1945. U.S. Army Air Forces/Library of Congress/Handout via REUTERS.

An atomic bomb of the "Little Boy" type, the kind which detonated over Hiroshima, Japan, is seen in an undated photograph. Los Alamos Scientific Laboratory/Naval History and Heritage Command/Handout via REUTERS.

Devastation caused by an atomic bomb is seen in Nagasaki, Japan March 17, 1948. Department of Energy/Lawrence Berkeley National Laboratory/Handout via REUTERS.

Devastation caused by an atomic bomb is seen in Hiroshima, Japan in an undated photograph. War Department/U.S. National Archives/Handout via REUTERS.

Undated handout photo courtesy of the U.S. National Archives shows the aftermath of the atomic bomb which was dropped on Nagasaki on August 9,1945. A Roman Catholic cathedral can be seen on the hill in the background.