A short, sharp - er, Strategic? - defence review
OK, consider this. You are the pre-eminent military power in Europe. Suddenly out of nowhere you spot a "threat". But no worries: your officer corps is skilled in expeditionary warfare and you have the finest professional army in the world. You set your technologists off to develop new and secret weapons. Then you declare war on the "threat" at the first opportunity.
But the "threat" turns out to have three things you don't. A reserves system that can mobilise hundreds of thousands of trained part-timers; a railway system that can deliver them to the battlefield; and a level of social legitimacy for the military which your professionalised armed force never enjoyed.
Result: within six weeks your head of state is a POW and your army has surrendered. Within six months your capital city is surrounded by the "threat" and ruled by armed insurgents.
That is the story of France in the Franco-Prussian war, which was won, effectively, at the design stage between two military systems.
After the election, the UK armed forces will once again be going through a design stage, and in a world where threats are hard to predict.
There will be a Strategic Defence Review, 12 years on from the last, which is still worth a read as an example of how hard it is to anticipate a threat. The word "terrorism" appears 13 times in the document, almost always in a list of potential threats that goes: "drugs, terrorism and crime". The word Afghanistan appears once, in relation to heroin supply. There is no mention of Islamism or jihad.
The timescale for the upcoming SDR is looking very crushed. I understand both Labour and the Conservatives see the Strategic Defence Review as needing to be complete by the time of the departmental spending review they plan in October/November.
I also understand that, for the Conservatives, in addition to the usual efficiency savings and the perennial problem of the MoD's procurement culture, the issue of 1st Armoured Division in Germany is looming large.
The British Army has around 23,000 troops in Germany "facing nothing" as one senior Conservative put it to me. Though there would be a high upfront cost in moving or decommissioning this force it would have geo-political overtones as well, as the force forms the "framework nation" of the NATO Allied Rapid Reaction Corps, which is already moving its signals and logistics brigades back to the UK this year.
Labour meanwhile is also preparing to make "tough choices", though not necessarily the same ones. Here the dichotomy tends to be posed as "tanks versus digital warfare and drones" - but there is, I understand, a similar determination to get most of the big decisions done before the cuts packages are announced.
The problem is that some in the armed forces are looking for a more "strategic" and therefore more deliberate process to come out of the SDR.
There is the army-versus-navy lobbying effort that Newsnight has reported on before, essentially and argument about how much blue-water naval capability you need if your primary goal is to the ability to conduct expeditionary warfare.
But there is also some thinking going on in the UK Armed Forces about their role and "legitimacy" in society: that is, a much broader set of questions about the relationship between reserves and professional soldiers; military intervention versus stabilisation and humanitarian roles abroad; where soldiers and their families should live and who provides their health care etc.
Those I've spoken to are asking bigger questions than the politicians and over a longer time-horizon, in which the security threat to the UK may be very different to what it is now.
The Afghan deployment showed the UK's procurement system as out of step with the speed of change at the military level, leaving much of the kit to be procured out of "urgent operational requirement" budgets, and the long-term procurement plans needing hasty revision.
But the procurement process is only one part of the long-term agenda the SDR will have to address. The Defence, FCO and DFID budgets will be looked at as a whole under an incoming Conservative government's wider Security Review. But if the Institute for Fiscal Studies is right, we could be looking at a 25% real-terms cut whoever wins the election.
It is in this context that the SDR Green Paper, published in February, poses the following questions: what's the balance between defending the UK/ Europe and projecting force outside; if you do the latter, what kind of force do you need (ie do you need something like the US Marine Corps with one ethos for all its functions and one basic operational role); how do you square this with the armed forces' role in coping with disasters, terrorist attacks or banking collapse. Then, do you redraw the map of the NATO/EU command system and do you integrate forces more thoroughly within that?
I hear, among the military people I've talked to, a desire for these questions to be answered at the level of, well, strategy - by strategists. That is, politicians who take responsibility for designing armed forces that have the capability, wider societal support and resources for what they are going to ask them to do.
There is some doubt being expressed within the armed forces as to whether a process totally focused on delivering cuts by Christmas will deliver answers to these longterm questions.
Meanwhile there is also concern among civil servants - just as with the budget deficit issue - that if we get a hung parliament then none of the strategic decisions will get taken by the time the cuts have to happen.
One hundred years ago Britain was in the grip of a political debate about strategy which enthralled parliament and the popular press (the so-called "big navy" debate within Asquith's Liberal administration).
One byproduct of the parties' lack of candour about the cuts in general is that Labour and the Conservatives are keeping their detailed strategic defence proposals under wraps until after the election.
Whoever wins, finding out what is to be cut and why is going to be a signal moment of the next nine months.