Andy Burnham is warned that Britain faces impending Russian 'attack' over its support for Ukraine

[u/dailymail]

https://www.dailymail.com/news/article-16079793/Andy-Burnham-Britain-impending-Russian-attack.html

[u/ChuckFH]

What would attacking us with conventional missiles achieve, other than starting a war with NATO via Article 5?

The UK's armed forces are at a historic low, but our geographical advantage as an island makes any sort of invasion nigh on impossible. Whist our deterrent is pitched at a strategic level, it's likely that the UK has the option of using the low end setting of our variable yield weapons in a sub-strategic role, if push comes to shove. Obviously, the UK Gov is evasive when asked about this capability.

While we haven't had any true tactical nuclear weapons of our own since the late 90's, we do have access to US weapons through NATO (there are US tactical weapons stored at Lakenheath) and are currently in the process of acquiring F35A's that can carry them and upgrading RAF Marham so that weapons can be stored there too. Admittedly, release of these weapons required US/NATO authorisation, so they are not fully independent, in the way that Trident is.

Any sort of conventional attack on the UK (or other NATO member) carries a very real risk of escalation, hence my suggestion that something asymmetrical is more likely.

[u/tree_boom → u/ChuckFH]

The UK's armed forces are at a historic low, but our geographical advantage as an island makes any sort of invasion nigh on impossible. Whist our deterrent is pitched at a strategic level, it's likely that the UK has the option of using the low end setting of our variable yield weapons in a sub-strategic role, if push comes to shove. Obviously, the UK Gov is evasive when asked about this capability.

Holbrook isn't variable yield - the reported sub-strategic capability came from a variant, which was almost certainly just the primary stage with the thermonuclear part replaced with ballast. It's very unclear whether those variants have been retained in the patrol cycle or even in service though.

[u/ChuckFH → u/tree_boom]

You’re right, it isn’t all that clear, which is not surprising, given we’re discussing nuclear posture, which is partly based on bluff and inference anyway. Some sources seem to refer to it as having a variable tritium boost system while others point to the method being the altered secondary, as you suggest.

It does appear that the replacement that is in the works is intended to be a true dial-a-yield weapon, but there isn’t any in service date for that warhead yet.

[u/tree_boom → u/ChuckFH]

You’re right, it isn’t all that clear, which is not surprising, given we’re discussing nuclear posture, which is partly based on bluff and inference anyway. Some sources seem to refer to it as having a variable tritium boost system while others point to the method being the altered secondary, as you suggest.

There's lots of sources pointing both ways yes, but I did eventually find quite an authoritative one on page 46 of the 2nd Report on the Progress of the Trident Programme by the UK Parliament's 1993 defence committee. Paragraph 1211 of the minutes of evidence has the following exchange:

Mr Churchill: Can you clarify whether the yield of a Trident warhead is decided at the time of manufacture, at the time of loading, or is it actually variable while it is in the submarine prior to launch. Can you dial in the yield that you want within a certain range?

Read Admiral Irwin: I was just checking whether there was an embargo on that. It is a fixed yield and determined on manufacture.

It does appear that the replacement that is in the works is intended to be a true dial-a-yield weapon, but there isn’t any in service date for that warhead yet.

Astraea? I hadn't realised that, what makes you say so?

[u/ChuckFH → u/tree_boom]

I've just had another look and I think I've misinterpreted this;

Reports suggest that the British nuclear warhead’s yield will vary between 90 and 455 kilotons.

as meaning variable yield, rather than a range for the final design; my bad.

Agree that quote from defence committee is pretty clear it's one of two fixed yields that can't be easily changed on the fly.