It is said that Napoleon, on being told of the impressive attributes of a new general, asked, "But is he lucky?"
Napoleon, it seems, understood that in war, as in politics, luck - and timing - are everything.
Most politicians will ride their luck while they can but will come unstuck when their luck runs out. That is why Enoch Powell once said famously, and with only slight exaggeration, that "all political careers end in failure".
A case in point is that of Hekia Parata. She is a politician who enjoyed a meteoric rise. The problem with meteoric rises, however, is that it is all too easy. There isn't time to develop the calluses, the scar tissue, the thick skin, that will be needed when the going gets tougher.
Ms Parata had everything going for her. She had had a successful career outside politics.
She attracted attention by fighting a skilful by-election campaign in a hopeless seat so that she was a shoo-in for a National list seat and an apparently effortless rise - after effective spells deputising for others - into the Cabinet.
In John Key's new Cabinet, she seemed a natural for the hitherto problem portfolio of education. But just a year into her brief, she is in trouble. What went wrong? The short answer is that her luck ran out and the attributes that had served her well on the rise were not enough to sustain her when she came under pressure. But the story is a little more complicated than that.
Such is the flak she is now taking that it is easy to forget that her predecessor, Anne Tolley, had an equally difficult time. Those tribulations afflicting two education ministers in succession reflect not so much the particular deficiencies of the individual ministers as the deep flaws in the education policy pursued by the Government as a whole.
The Key Government has quite deliberately set out on a policy that flies in the face of our long and largely successful experience in creating an excellent education system in this country. The Government has preferred to play upon the fears, prejudices and just plain ignorance of some parents and - in the course of putting in place policies such as national standards - defied the evidence and the accumulated expertise of education professionals and experts from both at home and overseas.
Little wonder that conflict has been the leitmotif of education policy and that education ministers have struggled.
Hekia Parata was on a hiding to nothing, but - anxious to please - she did not have the political weight to defy the Prime Minister and avoid the obvious bear traps.
In this, she was not helped by the fact that she was saddled with a chief executive whom she had had no say in appointing. Lesley Longstone was a victim - as were we all - of a syndrome that is now well entrenched - the apparent belief that a half-way competent UK public official with little chance of reaching the top in Britain (as witness the willingness to come to New Zealand) would be good enough to do a wonderful job for us.
Never mind that knowledge of New Zealand and of our particular requirements might be lacking. The only criterion that matters, it seems, is that the appointee should have demonstrated commitment to the correct ideological positions - should (in Mrs Thatcher's term) be "one of us".
If actual experience applying "free-market" policies could also be shown, even if that experience had demonstrated the failure of such policies in Britain, so much the better. So, Hekia Parata found herself leant on from above and pushed further in the same direction from below. And, to make matters worse, she found herself committed by no less an educational expert than John Banks to an education experiment with so-called "charter" schools that even the Treasury has condemned as unwise.
When things turn sour, everything is seen in a bad light. When the minister ventured to hope that teachers might pronounce their pupils' names correctly - something that, as someone whose surname is consistently mispronounced, she no doubt felt strongly about - that was seen as arrogant and inappropriate.
And, as she came under pressure, she might have done well to recall the story told by Harold Macmillan, the former British Prime Minister. As a young MP, he revealed to a senior colleague that he was extremely nervous about speaking in the House of Commons, with "the enemy" facing him across the Chamber. "But," said the senior man, "those aren't your enemies. They're your opponents. Your enemies sit behind you."
Those who rise quickly will inevitably arouse less than generous feelings in those whom they overtake. As Hekia Parata's bubble has burst, it is equally inevitable that there should be some schadenfreude on the part of others and perhaps less disposition to help and support her.
So, the minister is pretty much on her own. Politicians, whether going up or down, don't usually attract much sympathy. But they are, after all, human. As Shakespeare might have observed, if you prick them, do they not bleed?
Bryan Gould is a former Labour MP in Britain and a former law don at Oxford University.