My points were:
1. I'll take an umbrella should it rain. The meaning of should is much closer to if than in case.
Really? I'm very surprised you'd think that.
2. When I spoke of a possible eventuality I was contrasting it with your certain eventuality. I was probably unclear. I meant to imply conditionality.
I was using
certain in the sense of 'particular'. The government is preparing for a particular eventuality or outcome.
I have found a number of grammarians (see below) who associate should + S-V inversion with conditionality. So far I have found none who equate it with in case.
Aarts (2011.291, )Carter & McCarthy (2006.756), Greenbaum (1996.341), Huddleston & Pullum (2002.188), Leech (2004.120), Quirk et al (1985.1094), Zandvoort (1972.219).
First, I can't see how this is about grammar. This is about meaning, and I think we ought to stick with our original example, the meaning of which is quite clear, don't you think?
I'm not sure what your understanding of this matter is. Do you mean to suggest that
if is correct in this context and that it has the same meaning as
should? Or do you mean that the sentence
doesn't have the sense that the government is making preparations in case diplomacy fails? Is your list of books a way of claiming that
should never has a sense of
in case-ness? Please clarify.
Here is the original text of an American correspondent:
NEW: A US official tells me, "The United States is concerned that the Russian Government is preparing for an invasion into Ukraine that may result in widespread human rights violations and war crimes should diplomacy fail to meet their objectives."
Sorry, I'm lost now. This is a completely difference sentence with a very different meaning. Where did you see the original sentence? Which sentence do you want to understand?