The report suggests that Roosevelt's supposed accidental use of the term"unconditional surrender" and his subsequent failure to back down played a significant role in shaping the strategy that led to the launch of atomic bombs on Japan. I found this claim hard to believe – and after some research, I think it's probably not correct.

Quite amazingly, the term ‘unconditional’ only entered into the Allied demands due to a verbal mistake made by Roosevelt when reading a joint statement in a live broadcast in January 1943, a fact that he later admitted.${}^{87}$ Churchill immediately repeated the demand, later saying: ‘Any divergence between us, even by omission, would on such an occasion and at such a time have been damaging or even dangerous to our war effort.'${}^{88}$ Thus, the otherwise reasonable idea that the bombs needed to be dropped to avoid more deaths in an invasion, was only true due to an unreasonable demand that was created by an error people were too proud to step back from. (Lessons from the development of the atomic bomb, page 27)

The claim is repeated on page 35. I couldn't easily find a copy of the original source for the claim^[1].

But I could find three sources that seem to refute this interpretation.

The first non-primary source argues that Roosevelt supported the "unconditional surrender concept".

The matter was also discussed in the fall of 1942 by the U.S. Chiefs of Staff who, at the end of December, recommended to the President that no armistice be granted Germany, Japan, Italy, and the satellites until they offered the "unconditional surrender" of their armed forces. The President in reply informed them on January 7, 1943 that he intended to support the "unconditional surrender concept" at the forthcoming Conference at Casablanca. (Balfour, 1979. Page 283)^[2]

Secondly, Churchill sent the following report on January 20th, 1943 in Casablanca - just four days prior to Roosevelt’s alleged "verbal mistake".

6. We propose to draw up a statement of the work of the conference for communication to the press at the proper time. I should be glad to know what the War Cabinet would think of our including in this statement a declaration of the firm intention of the United States and the British Empire to continue the war relentlessly until we have brought about the “unconditional surrender” of Germany and Japan. The omission of Italy would be to encourage a break-up there. The President liked this idea, and it would stimulate our friends in every country. ^[3]

(Churchill and Roosevelt were apparently confused about the specific procedures that should have led to the use of the term ‘unconditional surrender. So that might be part of the reason why they gave different accounts over time.^[4])

Thirdly,  Roosevelt likely held Press Conference Notes that were drafted between 22. and 23. January 1943 during his statement on the 24. January 1943.^[5] These notes called for the "unconditional surrender" of Germany, Japan, and Italy.

The President and the Prime Minister, after a complete survey of the world war situation, are more than ever determined that peace can come to the world only by a total elimination of German and Japanese war power. This involves the simple formula of placing the objective of this war in terms of an unconditional surrender by Germany, Italy and Japan. Unconditional surrender by them means a reasonable assurance of world peace, for generations. Unconditional surrender means not the destruction of the German populace, nor of the Italian or Japanese populace, but does mean the destruction of a philosophy hi Germany, Italy and Japan which is based on the conquest and subjugation of other peoples.

Based on this information, the timeline appears to be the following:

• 07.01.1943 – Roosevelt expresses support for the "unconditional surrender concept".
• 20.01.1943 – Churchill proposes using "unconditional surrender" in a statement, and notes that the President [Roosevelt] liked the idea.
• 22.-23.01.1943 – Press Conference Notes drafted that call for the unconditional surrender of Germany, Italy, and Japan.
• 24.01.1943 – Roosevelt uses the term "unconditional surrender" in his statement, likely holding Press Conference Notes in his hand, that exactly asks for the same.

From this sequence of events, it does not appear that Roosevelt used the term mistakenly. If so, this anecdote likely doesn't serve as an example of a slip-up and subsequent reluctance to back down from a mistake having severe consequences.

It's also well possible that I'm missing something here. Would love to learn more.

1. ^{^}

   Rhodes, Richard. 1986. The Making of the Atomic Bomb.

2. ^{^}

   Balfour, M. (1979). The Origin of the Formula. Armed Forces & Society, 5(2), 281–301.

3. ^{^}

   Churchill, Winston. 1950. Second World War: The Hinge of Fate Hardcover (pages 834 and 835)

^{^}

Balfour (1979) has a confusing passage about the second explanation:

"When the draft of the Casablanca communiqué was submitted to Roosevelt and Churchill, it contained no reference to unconditional surrender and neither leader seems to have queried the omission. The obvious reason was that Roosevelt instead mentioned it in his talk to the press. After Churchill's telegram to the Cabinet came to light, thus making it impossible to attribute his claimed surprise to the contention that the subject had not been discussed beforehand with him, the inference seems to be that the surprise lay in this manner of publication.
But the talk to the press was itself based upon a written text and one of the surviving drafts for this contains emendations which are said to be in Churchill's own hand, and must have been made during the preceding forty-eight hours. 13 Either he did not read the draft carefully, or his memory slipped, or else he, like Roosevelt, wanted to cover his tracks. It is unlikely that we will ever know the exact truth."

^{^}

Footnote 1: 

"Photographs of the Roosevelt–Churchill press conference of January 24, 1943, such as that following p. 483, show Roosevelt holding a document, presumably the notes printed here.

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