War breaks out; both the Americans and Russians

realise the possibilities of an atomic bomb.


2 August

Albert Einstein writes to president Roosevelt, telling him that it would be possible to build an atomic bomb.



US scientists begin work on an atomic bomb – Russian spies immediately begin sending detailed technical data to the NKVD.

6 December

President Roosevelt authorises the building of an atomic bomb.



Russian scientist Georgii Flerov warns Stalin that western scientists are developing an atomic bomb.

Manhattan Project – US begins work on the atomic bomb.


The US government sets up the ‘Manhattan Project’ to develop an atomic bomb.  Robert Oppenheimer is appointed Scientific Director.

The Soviet Unions begins work on an atomic bomb; progress is slow.


11 February

Stalin authorises the development of an atomic bomb and puts Kurchatov in charge.  At first he is not shown the NKVD’s spy reports; the work is underfunded, and progresses slowly.

Good progress in America; Russia lags behind, even though spies are reporting technical details.

5 May

It is decided to use the first atomic bomb on Japan.


Soviet spy Klaus Fuchs is transferred to work on the Manhattan project; he supplies detailed information to the NKVD.  The NKVD does not act because they did not understand the mathematics!


1 August

Americans capture Tinian (Japan within bombing range)

Iwo Jima; the Americans fear huge losses

if they attempt to invade Japan.



Americans capture Iwo Jima but with huge losses; the Japanese defenders resist fanatically.


27 April

US identifies Hiroshima as the target city.

Germany surrenders.

7 May

Germany surrenders – end of the war in Europe.




26 May

Tokyo destroyed by US firebomb raid; Japan does not surrender.

13 July

First Japanese offer (through their ambassador in Russia) about making peace.

16 July –


Potsdam Conference

Successful US atomic test.

16 July

‘Trinity’ test at Alamogordo, New Mexico successfully tests an atomic detonation.  J. Robert Oppenheimer says: "I am become death, the destroyer of worlds." 

Ethical debate in the US about whether and how

to use the Bomb.

17 July

155 Manhattan Project scientists petition Truman to give Japan an opportunity to surrender before he uses the Bomb.

18 July

Truman tells Churchill about the Bomb; they agree to tell Stalin.

Stalin tells Truman and Churchill that the Japanese had asked for peace.

21 July

Truman authorises use of the Bomb.

Truman ‘sort of’ tells Stalin about the atomic bomb.

24 July

Truman tells Stalin that the US has "a new weapon of unusual destructive force."  Stalin appears not to understand the implications, but immediately orders Soviet scientists to invent their own atomic bomb.




25 July

Truman insists on a military target (later it was claimed that Hiroshima was a military target).

26 July

The Potsdam Declaration calls upon Japanese "to proclaim now the unconditional surrender of all Japanese armed forces." 

On the same day, the Japanese again tried to arrange peace negotiations through their ambassador in Moscow.

28 July

Japan officially rejects the Potsdam Declaration

A Japanese offer of peace is ignored.

3 August

Truman informed that the Japanese were again asking for peace


6 August

Hiroshima; Truman  calls it ‘the greatest day in history’




7 August

Russia enters the war in the Pacific, a week ahead of schedule.

9 August


14 August

Japan surrenders