probably nothing...

[pars]

Dear everybody!
What is the exact meaning of the phrase in bold? It is from the book “Persian Gulf Command” by Ashley Jackson, p. 204. Of course, its meaning is clear, bit its relationship to the whole paragraph, I mean its role, is ambiguous for me.

Cripps replied to Eden on the same day, 25 October 1941. He reported that the feeling in Soviet government circles and among the population as a whole about the lack of armed help from Britain ‘is very strong indeed’. Diplomatic relations were worsening, and ‘probably nothing less than the dispatch of a force not less than a corps’ and RAF resources ‘is our only hope of checking a dangerous deterioration, not only in the will of the Russians to resist, but also in our relations with the Soviet Government . . .
Many thanks in advance.

[Piscean]

Cripps replied to Eden on the same day, 25 October 1941. He reported that the feeling in Soviet government circles and among the population as a whole about the lack of armed help from Britain ‘is very strong indeed’. Diplomatic relations were worsening, and probably sending a minimum force of not less than a corps’ and RAF resources ‘is our only hope of checking a dangerous deterioration, not only in the will of the Russians to resist, but also in our relations with the Soviet Government . . .

Does that help?

Cripps is telling Eden that he needs to send a large military force in order to encourage the Russians to resist and to improve relations with the Soviet government.

[Charlie Bernstein]

It's awkward phrasing, isn't it? Two less thans in one sentence require a lot of untangling.