260 Mr S. M. Bruce, High Commissioner in London, to Mr R. G. Menzies, Prime Minister
Cablegram 344 LONDON, 22 May 1940, 3.30 a.m.
FOR PRIME MINISTER PERSONAL HIMSELF
As the occupation by the Germans of the Channel Ports is a definite possibility  it is necessary to consider the position which would face us in such event.
It will almost certainly be followed by an intensive air offensive against United Kingdom which while being extremely unpleasant and possibly tragic will probably only strengthen the determination of the people. It may however by destruction of factories and general slowing up of production seriously reduce output of aeroplanes.
As our reply to German air attacks must be prompt retaliation by sustained air offensive against Germany this most serious.
In fact if necessary supplies of Bombers for this purpose and of fighters to meet German attacks upon United Kingdom cannot be maintained it is impossible to forecast what position might develop here.
The only source from which these supplies can be obtained with sufficient rapidity is from America and then only by the United States of America handing over planes already delivered to and planes coming to hand in the near future for their own Air Force.
In view of the prospect of the Germans at the Channel Ports and the not inconceivable possibility of a French collapse under further successful pressure by the Germans it seems to me that the time has come when the possibilities in their naked hideousness will have to be put to Roosevelt.
I understand that Prime Minister  has been in personal communication with Roosevelt but I gather to date without convincing him of the vital necessity of immediate U.S.A.
assistance even to the point of drawing on their own defence equipment. I suggest that the urgency of the position might be brought home to him if you and Smuts  added your support to the efforts the Prime Minister is already making. There is no doubt the young democratic Dominions have an appeal of their own both to Roosevelt and the American people.
The following are some of the points that would have to be put to Roosevelt:-
That the French may be militarily defeated.
That in such event our power to resist and eventually defeat the enemy will depend on the continued exercise of our sea power and our ability to prevent the air domination of the United Kingdom by Germany.
Our capacity to do these things is dependent on our having adequate air strength. Starting with a numerical inferiority that strength might be so reduced by attrition and interference with our production and capacity to replace as to render us incapable of either exercising our sea power successfully or preventing the air domination of the United Kingdom by Germany.
In such event the possibility of our either (1) having to move the seat of Government from and ceasing to base the British Fleet on the United Kingdom or (2) having to come to terms with the Germans cannot be ignored.
An examination of (1) reveals grave problems with regard to the British Fleet apart from the difficulties of adequate bases for maintaining refitting etc. The primary value of the Fleet is to deny to the enemy vital and necessary supplies by its control of the seas. With the whole of Europe under German domination the only vital supplies we could deny her would be food and oil. With regard to the former a serious blockade would probably mean starvation not for the Germans but for the unfortunate country she has invaded. With regard to the latter all her needs could be met by over-running Iran and Irak an operation notwithstanding the possibility of opposition by Russia and/or Turkey she would probably be in a position successfully to undertake. It is therefore difficult to see how the continuance of the struggle by the removal of the seat of Government and of the British Fleet would advantage the United Kingdom. It would preserve the rest of the Empire but at a hideous cost to the United Kingdom.
On the other hand the prevention of the British Fleet falling in to German hands is of vital importance to the United States of America.
It therefore seems to me that the position should be put to Roosevelt without any toning down of its darker shades and he should be made to realise that unless assistance is given immediately with aeroplanes there is grave danger of the position so developing that the British Government will be compelled to come to terms with the Germans who would demand as the basis of any agreement the surrender of the British Fleet and the handing over of the West Indian Islands.
On the other hand the picture should be drawn of our capacity to meet all attacks against the United Kingdom, to undermine the morale of the German people and to inflict such material damage particularly on oil supplies and oil production plants by continuous air offensives as to bring about the defeat of the enemy provided the U.S.A. is prepared to supply the additional aeroplanes required.
In my view in handling the U.S.A. it will be necessary to make clear our preparedness while safeguarding the future against further aggression to face the problems of social and economic reconstruction in a spirit of liberal and generous co-operation.
The suggestions above as to possible future war developments are of course not a forecast of what I believe will happen but are only an appreciation of possibilities which we would be unwise to ignore. 
If any of above thoughts appeal to you I suggest your immediately communicating with Prime Minister here and Smuts as to desirability of approach to Roosevelt and whether communications should be joint or several.