Is it OK to bend or break peacetime rules at time of war?
Yes most definitely but only with support from on high and for sensible, operational tasks. I can only speak for my fleet (C130) but if they applied all the peace time 2Gp rules to our current deployments then there would be no flying at all. Ever. Shared rooms, no meals, disturbed sleep etc etc. Crews generally get on and do the job because they can appreciate that the peace time GASOs are overly restrictive and that many of them can't and shouldn't apply in an operational theatre. The flip side of this however is that crews must be able to recognise their own limits and balance those against noddy tasking like shifting another pallet of pallets to BSN and back and be able to say no where appropriate/necessary.
I generally try and remind myself what part it is my sortie plays in the grand scheme of things, what impact my saying no would have on ops and balance that against how tired etc I actually am. People that get precious about crew duty/rest and try and apply the minutiae of the regs generally need to have a bit of a chat with themselves and perhaps should be reminded of what it is they're involved in. Interestingly they're generally the people who will happily smash it up til all hours on a Vegas nightstop without subsequent complaint.
Any gibbon can quote the rule book but an effective, military operator in a time of war needs to be able to interpret and apply them realistically to ensure that the job gets done. At the same time, the command chain (and support staff) need to recognise this and ensure that the tasking given to crews is sensible and that at least a modicum of thought has gone into it (to be honest, this is where these things generally fall down with crews facing poorly thought out loads and pointless repetitive re-roles).
If you're not able to interpret and effectively apply the rules in a time of high tempo ops then poke off to EasyJet or 216
PS. As for the chap and his A340, he should have said no but one would have to ask why he'd only had 3.5hrs sleep. If the company had put him in a hotel that was still being built or was over a nightclub then it's easier to say no and lay it at the feet of the company. If however he'd been on the lash or deliberately chose to engage in activities that prevented him sleeping then would have question his suitability to command large jets full of people...