Back then, it quickly became evident the US under Bush Senior was wholly determined to retake Kuwait, by force if necessary; and that the Brits would pitch in strongly - Mrs T, beleagured by the Poll Tax fiasco (Michael Portillo, where are you now?), was still PM and had long been looking to replicate the Falklands Factor.++
In 1990 I was a reservist. The rules for mobilisation of reserves in those days were very restrictive (the later conflicts of the 1990s saw them greatly "relaxed", if that's the right word) - it could only be ordered if the UK itself or NATO was under a concrete military threat to its own territory. However, I was a specialist and the rules had long since been waived for us, on a volunteer basis (I have no idea whether ministers had been informed ...). And the cause was just.
Also, at the time I was working for a US oil company(!) who were, *ahem*, entirely supportive of releasing me for a while. There was an immediate ramping-up of UK crisis plans, which called for the rapid build-up of various normally dormant HQ operations. Partly this could be achieved by switching regular officers out of their peacetime roles: but it was also handy to have suitably qualified reservists available. I had the experience - and a high security clearance. So, back to the Colours I went ... (TBC)
** The UK is considerably more
++ History Corner has another story to tell on that front ...