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163 Lord Cranborne, U.K. Secretary of State for Dominion Affairs, to Mr John Curtin, Prime Minister

Circular cablegram M426 LONDON, 5 December 1941, 8.20 p.m.


Following for the Prime Minister:-

My Circulars M.418 [1] paragraphs 3-5, M.421 paragraph 7 [2], and
M.422 [3] [paragraph 5]. [4]

1. We have explained to His Majesty's Minister at Bangkok [5] for
his most secret and personal information the nature of the Kra
Isthmus plan and the circumstances in which it would be put into
operation. We are also consulting him on the following lines:-

(1) It is important that if and when the operation is carried out
it should not meet with Thai resistance. It is in our view our
best first strategic move in circumstances envisaged, not
excluding further possibilities, and represents the best means of
helping Thailand.

(2) We have it in mind therefore in order to prepare the way to
give Thailand an assurance that in the event of a Japanese attack
we will help them to the best of our ability. [6]

(3) We hope that this promise of assistance might encourage
Thailand to resist Japan and that the Thailand Government if
compelled to abandon Bangkok would transfer themselves to British
territory while their troops retired southwards to link up with
our own.

(4) We understand the Thai position to be that no military
arrangement of any kind is practicable without a definite warning
to Japan by the United States and ourselves. [7] We are consulting
the United States Government about the possibility of a warning,
but Sir J. Crosby should make no approach to the Thai Government
pending further instructions.

2. A further telegram will be sent on the receipt of Sir J.

Crosby's reply. In the meantime we have informed His Majesty's
Ambassador at Washington [8] that we are consulting Sir J. Crosby
in this sense. We hope (see paragraph 5 of Circular M.422) that
the United States Government may feel able to join with us in the
assurance as in paragraph 1 (2) above.

1 Document 157.

2 Dispatched 4 December. On file AA:A981, Japan 178. Paragraph 7
referred to President Roosevelt's suggestion that the U.K. Govt
should indicate both privately to the Thai Govt and publicly that
it had no intention of invading Thailand but was concerned to see
her sovereignty and independence preserved.

3 Dispatched 5 December. On file AA:A981, Japan 185B, iii.

4 Inserted from the London copy on file AA: A2937, Japan-America 8
March -9 Dec 1941. Paragraph 5 referred to the technical
difficulty involved in giving the Thais a guarantee of non-
aggression when the U.K. Govt's proposed action in Thailand was of
a forestalling nature.

5 Sir Josiah Crosby.

6 On 4 December (cablegram 879 on the file cited in note 2) Crosby
had informed the Foreign Office of his growing impatience with the
'unwillingness ... of either London or Washington to give Thailand
a clear cut promise of military support in the event of a Japanese
invasion' and of the expectation of the Thai public that such
support would be forthcoming. His views were shared by the U.S.

Minister to Thailand (Hugh G. Grant), who was cabling Washington
in the same sense.

7 On 4 December Crosby had reported that the Thai Foreign Minister
(Nai Direk Jayanama) had 'pressed me very urgently indeed this
morning for an immediate declaration from us to Japan that she
would find herself at war with us if she attacked Thailand. He
said that he had spoken to the United States Minister in the same
sense' (see cablegram 886 to the Foreign Office on the file cited
in note 2). On 5 December Crosby cabled again that he had received
an 'urgent appeal from the Thai Prime Minister [Maj Gen Luang P.

Pibulsonggram]', who expected a Japanese attack 'within the next
few days' and begged 'most earnestly for immediate public
statement by His Majesty's Government that Japan will find herself
at war with us if she attacks Thailand' (see cablegram 890 to the
Foreign Office on file AA:A981, Japan 174, iii).

8 Lord Halifax.

[AA: A981, JAPAN 174, iii]
Last Updated: 11 September 2013
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